After upgrading to the latest of Laserfiche Forms 12, when I browsed to /FormsConfig I received an error message that said that ""Login failed for user 'DOMAIN\SERVERNAME$'.". It didn't give any information if that was the Windows Service or the IIS App Pool. I found that it was the App Pool and updated the Identity and it worked, but it would have been nice if the error message mentioned what it was referring to.