How To Fix Nintex Workflow Activation Error

Enabling Nintex Workflow Feature failed

I wanted to Enable the Nintex Workflow Features for the newly created web application. The moment selects the web application and click ok to Activate the feature, below error appeared.

Different Posts on Nintex Community was saying different options for the same error. On of those was database Logical name was different than source Farm DB. But in my case even I make database logical names same, it did not work for me.

Then I had to check with Nintex Support for further details and they helped me to get the solution

Sorry, something went wrong

Warning: Unable to add the application pool account to the Nintex Workflow database. If you have permissions problems, contact support@nintex.com for assistance.

Technical Details

Troubleshoot issues with Microsoft SharePoint Foundation.

Correlation ID: be63519f-6822-4080-8d49-03863e6e0832

Date and Time: 5/11/2020 6:06:34 PM

This was due to two reasons

1.  Farm account did not has enough permission for the Nintex config database. Error was in ULS As follows 
1. Permission Error :Cannot open database "Nintex Config DB Name" requested by the login. The login failed. Login failed for user “domain\farm account”.

2. Solution:  Provide WSS_Content_Application_Pools db permission for Farm account on Nintex Config Database
2. Nintex Configuration Database was not getting updated with the new DB Server Name on dbo.Databases Table.
1. Root Cause :When attached an existing configuration database to the Upgraded SharePoint farm, Nintex was failed to update the New DB Server Name in Databases table in Nintex Config Database.

2. Solution: Update the ServerName Column on dbo.Databases Table on config Database with Actual DB Server name or SQL Alias you have used in the farm.