Travel Authorization Could Not be Approved

Hi

When I add a custom user list of SQL to delivered notifications final approver not able to approve transaction.

Error:

Approver Receives mail with  'Travel Authorization Could Not be Approved'

Replication Scenario:

1..Created a user list based on SQL

2.Added the user list to 'On Final Notify' along with delivered user list remains along with Custom.

3.On Final Approval users receiving error mail.

Note: Except in production no other instance we are able to replicate the same.