Need help on Exchange 2016 monitoring

I'm trying to configure my last exchange server to be monitor in SAM, but it's giving me very weird error. I've tried countless way to troubleshoot &  now hitting a road block. Did anyone face the same problem as mine?

Basically when I added the credentials in App monitor, the test shows success, however when I click Configure Server it's giving error saying my account is not an Active Directory account. Hello... if it's not an active directory account WTH is the test is passing.

Below is the screenshot. 


Did I say my last exchange server? Yes! the first exchange server was added without any hiccups, I follow the exact similar steps for my last exchange servers but that didn't work.

Please Help!!! I'm pulling my hair out trying to figure what went wrong.