"Access denied" when publishing a Nintex Forms after applying a Sharepoint CU.

Issue

When publishing or saving a Nintex Form after applying a security update to the SharePoint servers, it is possible to obtain an Access Denied error. 

Resolution

1. Clear the SharePoint Configuration Cache,  link on how to clear the cache https://community.nintex.com/t5/How-To-s/Clearing-SharePoint-Configuration-Cache/ta-p/86252
2. If the issue is occurring following a SharePoint Cumulative Update, run the SharePoint Configuration Manager (or PSCONGIF.exe) using set up account.
3. Reboot all servers in the environment
4. Add the Web Application Pool Service Account to wss_admin_wpg group on all servers
5. Update Nintex Forms in the farm (In case the issues doesn't resolved after adding the App Pool account to the wss_admin_wpg group)

Additional Information

Make sure first the App Pool account of the Web Application is part of the wss_Admin_wpg and try publishing the form in case it was missing on any servers before executing all the steps on point 1. 

Message from Nintex Forms Designer:

The server encountered an error processing the request. The exception message is 'Access is denied.'. See server logs for more details.

Note: The above message may be surrounded with raw HTML, making it difficult to read initially.

Message from the ULS Log:
Failed to Publish Nintex Form. Error: Access denied