Wrong API key results in fatal error – how to fix

Ran into the same issue.

We where trying to set it up using the PayPal Sandbox Business Pro account

We will keep looking into it but hope this helps

The reply was

["body"]=>
  string(77) "{"error":"invalid_client","error_description":"Client Authentication failed"}"
  ["response"]=>
  array(2) {
    ["code"]=>
    int(401)
    ["message"]=>
    string(12) "Unauthorized"
  }

Error

2021/07/22 20:04:56 [error] 83366#83366: *125028 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught WooCommerce\PayPalCommerce\ApiClient\Exception\RuntimeException: Could not create token. in /www/localhost/public/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-api-client/src/Authentication/class-paypalbearer.php:122
Stack trace:
#0 /www/localhost/public/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-api-client/src/Authentication/class-paypalbearer.php(97): WooCommerce\PayPalCommerce\ApiClient\Authentication\PayPalBearer->newBearer()
#1 /www/localhost/public/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-wc-gateway/src/Settings/class-settingslistener.php(150): WooCommerce\PayPalCommerce\ApiClient\Authentication\PayPalBearer->bearer()
#2 /www/localhost/public/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-wc-gateway/src/class-wcgatewaymodule.php(236): WooCommerce\PayPalCommerce\WcGateway\Settings\SettingsListener->listen_for_vaulting_enabled()
#3 /www/localhost" while reading response header from upstream, client: 98.0.35.41, server: localhost.dev, request: "GET /wp-admin/admin.php?page=wc-settings&tab=checkout&section=ppcp-gateway HTTP/1.0", upstream: "fastcgi://unix:/var/run/php7.4-fpm-localhost.sock:", host: "localhost.dev", referrer: "https://localhost.dev/wp-admin/admin.php?page=wc-settings&tab=checkout"

### WordPress Environment ###

WordPress address (URL): http://localhost.dev
Site address (URL): http://localhost.dev
WC Version: 5.5.1
REST API Version: ✔ 5.5.1
WC Blocks Version: ✔ 5.3.2
Action Scheduler Version: ✔ 3.2.1
WC Admin Version: ✔ 2.4.1
Log Directory Writable: ✔
WP Version: ❌ 5.7.2 - There is a newer version of WordPress available (5.8)
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: –
WP Cron: –
Language: en_US
External object cache: –

### Server Environment ###

Server Info: nginx/1.21.0
PHP Version: 7.4.21
PHP Post Max Size: 128 MB
PHP Time Limit: 300
PHP Max Input Vars: 10000
cURL Version: 7.68.0
OpenSSL/1.1.1f

SUHOSIN Installed: –
MySQL Version: 5.5.5-10.5.10-MariaDB-1:10.5.10+maria~focal-log
Max Upload Size: 128 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### Database ###

WC Database Version: 5.5.1
WC Database Prefix: wp_
Total Database Size: 5.27MB
Database Data Size: 3.34MB
Database Index Size: 1.93MB
wp_woocommerce_sessions: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_api_keys: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_attribute_taxonomies: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_downloadable_product_permissions: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_woocommerce_order_items: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_order_itemmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_tax_rates: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_woocommerce_tax_rate_locations: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_shipping_zones: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_woocommerce_shipping_zone_locations: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_shipping_zone_methods: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_woocommerce_payment_tokens: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_woocommerce_payment_tokenmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_woocommerce_log: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_actions: Data: 0.02MB + Index: 0.13MB + Engine InnoDB
wp_actionscheduler_claims: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_groups: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_actionscheduler_logs: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_ac_segments: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_admin_columns: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_commentmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_comments: Data: 0.02MB + Index: 0.09MB + Engine InnoDB
wp_gf_addon_feed: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_gf_draft_submissions: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_gf_entry: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_gf_entry_meta: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_gf_entry_notes: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_gf_form: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_gf_form_meta: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_gf_form_revisions: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_gf_form_view: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_gf_rest_api_keys: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_links: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_options: Data: 2.05MB + Index: 0.06MB + Engine InnoDB
wp_postmeta: Data: 0.06MB + Index: 0.06MB + Engine InnoDB
wp_posts: Data: 0.05MB + Index: 0.06MB + Engine InnoDB
wp_termmeta: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_terms: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_term_relationships: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_term_taxonomy: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_usermeta: Data: 0.03MB + Index: 0.03MB + Engine InnoDB
wp_users: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_wc_admin_notes: Data: 0.05MB + Index: 0.00MB + Engine InnoDB
wp_wc_admin_note_actions: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_wc_category_lookup: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_wc_customer_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_download_log: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_order_coupon_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_order_product_lookup: Data: 0.02MB + Index: 0.06MB + Engine InnoDB
wp_wc_order_stats: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_wc_order_tax_lookup: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_wc_product_meta_lookup: Data: 0.02MB + Index: 0.09MB + Engine InnoDB
wp_wc_reserved_stock: Data: 0.02MB + Index: 0.00MB + Engine InnoDB
wp_wc_tax_rate_classes: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_wc_webhooks: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_yoast_indexable: Data: 0.02MB + Index: 0.08MB + Engine InnoDB
wp_yoast_indexable_hierarchy: Data: 0.02MB + Index: 0.05MB + Engine InnoDB
wp_yoast_migrations: Data: 0.02MB + Index: 0.02MB + Engine InnoDB
wp_yoast_primary_term: Data: 0.02MB + Index: 0.03MB + Engine InnoDB
wp_yoast_seo_links: Data: 0.02MB + Index: 0.03MB + Engine InnoDB

### Post Type Counts ###

attachment: 2
customize_changeset: 2
nav_menu_item: 30
page: 29
post: 2
product: 1
product_variation: 2
revision: 23
wc_membership_plan: 1
wc_user_membership: 2

### Security ###

Secure connection (HTTPS): ✔
Hide errors from visitors: ✔

### Active Plugins (15) ###

Gravity Forms: by Gravity Forms – 2.5.7
Admin Columns Pro: by AdminColumns.com – 5.5.3
Advanced Custom Fields PRO: by Delicious Brains – 5.9.8
Akismet Anti-Spam: by Automattic – 4.1.10
Gravity Forms Event Tracking: by Ronald Huereca – 2.4.2
Hall Customization: by Hall – 1.20.0
Hall Mail: by Hall – 1.8.3
Privacy Notice: by Hall Internet Marketing – 1.0.0
Hall Updater: by Hall – 1.3.1
WooCommerce Memberships: by SkyVerge – 1.22.3
WooCommerce PayPal Payments: by WooCommerce – 1.3.2
WooCommerce Social Login: by SkyVerge – 2.11.0
WooCommerce Subscriptions: by WooCommerce – 3.1.3 (update to version 3.1.4 is available)
WooCommerce: by Automattic – 5.5.1
Yoast SEO: by Team Yoast – 16.7

### Inactive Plugins (7) ###

Google Listings and Ads: by WooCommerce – 1.2.1
Google Tag Manager for WordPress: by Thomas Geiger – 1.13.1
Teams for WooCommerce Memberships: by SkyVerge – 1.5.5
WooCommerce AvaTax: by SkyVerge – 1.13.0
WooCommerce Google Analytics Pro: by SkyVerge – 1.10.0
WooCommerce Stripe Gateway: by WooCommerce – 5.2.3
WooCommerce Subscriptions Gifting: by WooCommerce – 2.1.3

### Must Use Plugins (1) ###

Kinsta Must-use Plugins: by Kinsta Team – 2.3.6

### Settings ###

API Enabled: –
Force SSL: ✔
Currency: USD ($)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2
Taxonomies: Product Types: external (external)
grouped (grouped)
simple (simple)
subscription (subscription)
variable (variable)
variable subscription (variable-subscription)

Taxonomies: Product Visibility: exclude-from-catalog (exclude-from-catalog)
exclude-from-search (exclude-from-search)
featured (featured)
outofstock (outofstock)
rated-1 (rated-1)
rated-2 (rated-2)
rated-3 (rated-3)
rated-4 (rated-4)
rated-5 (rated-5)

Connected to WooCommerce.com: –

### WC Pages ###

Shop base: #7 - /shop/
Cart: #8 - /cart/
Checkout: #9 - /checkout/
My account: #10 - /my-account/
Terms and conditions: #42 - /terms-of-use/

### Theme ###

Name: localhost
Version: 3.2
Author URL: localhost theme
Child Theme: ❌ – If you are modifying WooCommerce on a parent theme that you did not build personally we recommend using a child theme. See: How to create a child theme
WooCommerce Support: ✔

### Templates ###

Overrides: –

### Memberships ###

Restriction mode:: Hide content only
Public content:: –
Excluded from discounts:: –
Membership plans:: 1
Individual:: Members: 0Access method: Product(s) purchaseAccess length: Unlimited Subscription: YesInstallment plan: No

### Subscriptions ###

WCS_DEBUG: ✔ No
Subscriptions Mode: ✔ Live
Subscriptions Live URL: https://localhost.dev
Subscription Statuses: –
WooCommerce Account Connected: ❌ No
Report Cache Enabled: ✔ Yes
Cache Update Failures: ✔ 0 failure

### Store Setup ###

Country / State: United States (US) — Illinois

### Payment Gateway Support ###

PayPal Standard: subscription_payment_method_change_customer
subscription_payment_method_change_admin
subscription_amount_changes
subscription_date_changes
multiple_subscriptions
subscription_payment_method_delayed_change
subscriptions
subscription_cancellation
subscription_suspension
subscription_reactivation
products
refunds

PayPal Reference Transactions Enabled: ✔ Yes

### Social Login ###

Facebook: ✔ Available
Twitter: Disabled
Google: ✔ Available
Amazon: Disabled
Linkedin: Disabled
Paypal: Disabled
Disqus: Disabled
Yahoo: Disabled
Vkontakte: Disabled

### Action Scheduler ###

Complete: 54
Oldest: 2021-07-22 16:15:01 +0000
Newest: 2021-07-22 20:00:01 +0000

Pending: 1
Oldest: 2021-07-22 20:04:47 +0000
Newest: 2021-07-22 20:04:47 +0000

### Status report information ###

Generated at: 2021-07-22 20:14:32 +00:00

It seems like the issue was the login process for the sandbox was unclear and entering the incorrect information in the manual process was causing the issue.

Additional checks/validation should be done on the information and documentation improved.

Otherwise should be all set now for me.

Hopefully the information above helps.

Awesome! Glad to hear it and thanks for the info.