WP-Give: PHP Fatal Error on confirmation screen

We are using a multi-page form for donations, everything works as expected until the payment is submitted. Then we get the following fatal error:

[02-Nov-2021 23:10:58 UTC] PHP Fatal error:  Uncaught Error: Class name must be a valid object or a string in /home/vps2020/2030orbust.org/wp-content/plugins/give/src/Form/Templates.php:112
Stack trace:
#0 /home/vps2020/2030orbust.org/wp-content/plugins/give/src/Form/Templates.php(98): Give\Form\Templates->getTemplateObject(false)
#1 /home/vps2020/2030orbust.org/wp-content/plugins/give/src/Controller/Form.php(125): Give\Form\Templates->getTemplate()
#2 /home/vps2020/2030orbust.org/wp-includes/class-wp-hook.php(287): Give\Controller\Form->loadDonationFormView('')
#3 /home/vps2020/2030orbust.org/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#4 /home/vps2020/2030orbust.org/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#5 /home/vps2020/2030orbust.org/wp-includes/template-loader.php(13): do_action('template_redire...')
#6 /home/vps2020/2030orbust.org/wp-blog-header.php(19): require_once('/home/vps2020/2...')
#7 /home/vps2020/2030orbust.org/index.php(17): require('/home/vps2020/2...')
#8 {main}
  thrown in /home/vps2020/2030orbust.org/wp-content/plugins/give/src/Form/Templates.php on line 112

This seems similar to the following, but we are not using the SG Optimizer plugin:
https://wordpress.org/support/topic/clean-installation-breaks-class-name-must-be-a-valid-object-or-a-string/

System report:

### WordPress Environment ###

Home URL: https://www.2030orbust.org
Site URL: https://www.2030orbust.org
WP Version: 5.5.3
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: ✔
WP Cron: ✔
Language: en_US
Permalink Structure: /%year%/%monthnum%/%day%/%postname%/
Show on Front: page
Page on Front: 2030 or Bust – We Have A Plan To End The Climate Crisis (#7804)
Page for Posts: Unset
Table Prefix Length: wp_dgmkwg_
Table Prefix Length: 10
Table Prefix Status: Acceptable
Admin AJAX: Accessible
Registered Post Statuses: publish, future, draft, pending, private, trash, auto-draft, inherit, request-pending, request-confirmed, request-failed, request-completed, refunded, failed, revoked, cancelled, abandoned, processing, preapproval, give_subscription

### Server Environment ###

Hosting Provider: DBH: mysql.2030orbust.org, SRV: www.2030orbust.org
TLS Connection: Connection uses TLS 1.2
TLS Connection: Probably Okay
Server Info: Apache
PHP Version: 7.3.24
PHP Post Max Size: 512 MB
PHP Time Limit: 120
PHP Max Input Vars: 1000
PHP Max Upload Size: 512 MB
cURL Version: 7.52.1, OpenSSL/1.0.2u
SUHOSIN Installed: –
MySQL Version: 5.7.28
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
gzip: ✔
GD Graphics Library: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### GiveWP Configuration ###

GiveWP Version: 2.16.1
GiveWP Cache: Enabled
Database Updates: All DB Updates Completed.
Database Updates: All Database Migrations Completed.
Database Tables: ✔ wp_dgmkwg_give_donors✔ wp_dgmkwg_give_donormeta✔ wp_dgmkwg_give_comments✔ wp_dgmkwg_give_commentmeta✔ wp_dgmkwg_give_sessions✔ wp_dgmkwg_give_formmeta✔ wp_dgmkwg_give_sequential_ordering✔ wp_dgmkwg_give_donationmeta✔ wp_dgmkwg_give_revenue
GiveWP Cache: Enabled
GiveWP Cache: ✔New Donation✔Donation Receipt✔New Offline Donation✔Offline Donation Instructions✔New User Registration✔User Registration Information✔Donation Note✔Email access❌Renewal Receipt Email❌Renewal Receipt Email❌Subscription Cancelled Email❌Subscription Cancelled Email❌Subscription Completed Email❌Subscription Reminder Email✔Subscriptions Email Access✔Subscription Payment Failed Email
Upgraded From: 2.13.2
Test Mode: Disabled
Currency Code: USD
Currency Position: Before
Decimal Separator: .
Thousands Separator: ,
Success Page: https://www.2030orbust.org/donation-confirmation/
Failure Page: https://www.2030orbust.org/donation-failed/
Donation History Page: https://www.2030orbust.org/donor-dashboard/
GiveWP Forms Slug: /donations/
Enabled Payment Gateways: Stripe - Credit Card, Offline Donation
Default Payment Gateway: Stripe - Credit Card
PayPal IPN Notifications: N/A
Donor Email Access: Enabled
Stripe Webhook Notifications: November 7, 2021 1:51 am

### Active GiveWP Add-ons ###

Give - ActiveCampaign: ✔ Licensed – by GiveWP – 1.0.1
Give - Recurring Donations: ✔ Licensed – by GiveWP – 1.12.6

### Other Active Plugins ###

ActiveCampaign: by ActiveCampaign – 8.1.7
Advanced post slider: by digontoahsan – 2.5.1
Akismet Anti-Spam: by Automattic – 4.1.8
ARVE Advanced Responsive Video Embedder: by Nicolas Jonas – 9.5.14
CMSMasters Contact Form Builder: by cmsmasters – 1.3.2
CMSMasters Content Composer: by cmsmasters – 1.2.9
CMSMasters Mega Menu: by cmsmasters – 1.2.0
Custom Share Buttons with Floating Sidebar: by WP Experts Team – 3.9.1
Disable Gutenberg: by Jeff Starr – 2.4
Duplicate Page: by mndpsingh287 – 4.3
Easy Updates Manager: by Easy Updates Manager Team – 9.0.7
Insert PHP Code Snippet: by xyzscripts.com – 1.3.1
JSM's Force HTTP to HTTPS: by JS Morisset – 3.4.1
LayerSlider WP: by Kreatura Media – 5.3.2
Redirection: by John Godley – 5.0.1
Smash Balloon Instagram Feed: by Smash Balloon – 2.9.3.1
Spotlight - Social Media Feeds: by RebelCode – 0.9.5
UpdraftPlus - Backup/Restore: by UpdraftPlus.Com, DavidAnderson – 1.16.47
Use Any Font: by Dnesscarkey – 6.0.4
WP Downgrade | Specific Core Version: by Reisetiger – 1.2.2

### Inactive Plugins ###

3D FlipBook - Lite Edition: by iberezansky – 1.10.14
ARI Fancy Lightbox: by ARI Soft – 1.3.8
Contact Form 7: by Takayuki Miyoshi – 5.3.2
Hover Effects Pack Pro: by Labib Ahmed – 1.0
Image Hover Effects Ultimate (Photo Gallery, Effects, Lightbox, Comparison or Magnifier): by Biplob Adhikari – 9.5.0
Password Protected: by Ben Huson – 2.4
PayPal Donations: by Tips and Tricks HQ, Johan Steen – 1.9.6
Revolution Slider: by ThemePunch – 4.6.9
Simple YouTube Embed: by naa986 – 1.0.8
Smooth Scroll Page Up/Down Buttons: by Mark Senff – 1.3
Tooltip CK: by Cédric KEIFLIN – 2.2.10
Ultimate Endpoints With Rest Api: by Dipankar Pal – 2.2.2
Vimeography: by Dave Kiss – 2.2.1
WooCommerce: by Automattic – 5.0.1
WPForms Lite: by WPForms – 1.6.5
WP Htaccess Editor: by WebFactory Ltd – 1.67
WP Responsive Recent Post Slider/Carousel: by WP OnlineSupport – 2.6
WP Simple Pay Lite: by Sandhills Development, LLC – 2.6.0
WP Simple Pay Pro: by Sandhills Development, LLC – 4.0.2
WP Simple Pay Pro 2: by Moonstone Media – 2.5.6
WP Simple Pay Pro 2 - Subscriptions Add-on: by Moonstone Media – 1.3.6

### Theme ###

Name: 2020 or Bust
Version: 1.0.1
Author URL: 
Child Theme: Yes
Parent Theme Name: Social Activity
Parent Theme Version: 1.1.6
Parent Theme Author URL: http://cmsmasters.net/

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