Proceed to Checkout not working after update

Hi
Updated to 2.6 onlt to find “Proceed to Checkout” page not working on Cart..
I have reverted back to 2.5.5 as I have a promotion running and cant afford downtime….
Here is current system Status

### WordPress Environment ###

Home URL: http://photographycoursesni.co.uk
Site URL: http://photographycoursesni.co.uk
WC Version: 2.5.5
Log Directory Writable: ✔
WP Version: 4.5.2
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: –
Language: en_GB

### Server Environment ###

Server Info: Apache
PHP Version: 5.6.22
PHP Post Max Size: 128 MB
PHP Time Limit: 120
PHP Max Input Vars: 3000
SUHOSIN Installed: –
MySQL Version: 5.6.28
Max Upload Size: 128 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### Database ###

WC Database Version: 2.5.5
:
woocommerce_sessions: ✔
woocommerce_api_keys: ✔
woocommerce_attribute_taxonomies: ✔
woocommerce_termmeta: ✔
woocommerce_downloadable_product_permissions: ✔
woocommerce_order_items: ✔
woocommerce_order_itemmeta: ✔
woocommerce_tax_rates: ✔
woocommerce_tax_rate_locations: ✔

### Active Plugins (30) ###

Coming Soon Page & Maintenance Mode by SeedProd: by SeedProd – 5.0.2
WP ConvertKit: by ConvertKit – 1.3.9
Custom css-js-php: by flippercode – 2.0.1
Disqus Comment System: by Disqus  – 2.85
Duplicate Post: by Enrico Battocchi – 2.6
Envato WordPress Toolkit: by Envato – 1.7.3
Event Tickets Plus: by Modern Tribe
Inc. – 4.2

Event Tickets: by Modern Tribe
Inc. – 4.2

Google Analyticator: by SumoMe – 6.4.9.7
Limit Login Attempts: by Johan Eenfeldt – 1.7.1
NextGEN Gallery: by Imagely – 2.1.43
Woocommerce Easy Checkout Fields Editor: by Parbat Chaudhari – 1.0.6
PixelYourSite Pro: by PixelYourSite – 2.3.2
Redirection: by John Godley – 2.4.4
Related Posts Thumbnails: by Maria Shaldybina – 1.4.0
SumoMe: by SumoMe – 1.13
The Events Calendar: by Modern Tribe
Inc. – 4.2

Thrive Visual Editor: by Thrive Themes – 1.200.9
UpdraftPlus - Backup/Restore: by UpdraftPlus.Com
DavidAnderson – 2.12.13.22

WooCommerce ConvertKit: by Nick Ohrn of Plugin-Developer.com – 1.0.2
WooCommerce AdWords Conversion Tracking: by Wolf+Bär GmbH – 1.3.1
WooCommerce Google Analytics Integration: by WooThemes – 1.4.0
WooCommerce: by WooThemes – 2.5.5
WordPress Importer: by wordpressdotorg – 0.6.1
Yoast SEO: by Team Yoast – 3.3.0
WP Crontrol: by John Blackbourn & Edward Dale – 1.3
WP-Mail-SMTP: by Callum Macdonald – 0.9.5
WP Date Remover: by Omar – 1.0
WP Rollback: by WordImpress – 1.3
Wufoo Shortcode Plugin: by Chris Coyier / Wufoo – 1.43

### Settings ###

Force SSL: –
Currency: GBP (£)
Currency Position: left
Thousand Separator: ,
Decimal Separator: .
Number of Decimals: 2

### API ###

API Enabled: ✔
API Version: 3.1.0

### WC Pages ###

Shop Base: #13 - /shop/
Basket: #15 - /cart/
Checkout: #17 - /checkout/
My Account: #19 - /my-account/

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name: Salient
Version: 7.0.8
Author URL: http://themenectar.com
Child Theme: ✕ – If you're modifying WooCommerce on a parent theme you didn't build personally
then we recommend using a child theme. See: How to create a child theme

WooCommerce Support: ✔

### Templates ###

Overrides: salient/woocommerce/cart/cart-shipping.php
salient/woocommerce/cart/cart-totals.php
salient/woocommerce/cart/cart.php
salient/woocommerce/cart/shipping-calculator.php
salient/woocommerce/checkout/form-checkout.php
salient/woocommerce/checkout/form-shipping.php
salient/woocommerce/checkout/review-order.php
salient/woocommerce/content-product.php
salient/woocommerce/content-single-product.php
salient/woocommerce/loop/add-to-cart.php
salient/woocommerce/single-product/product-image.php
salient/woocommerce/single-product/tabs/description.php
salient/woocommerce/single-product/tabs/tabs.php