If you see the "Error - User Credentials were incorrect" message while adding new programs to your EPA Pro integration, it's likely due to inaccurate credentials. Ensure the credentials entered for the connection at https://dsw.epapro.co.uk/ are correct. If sign-in fails with those credentials, this is likely the cause of the error.
Attempt signing in again after re-entering the accurate credentials and reloading the tenant's browser window.