MDS 2016 - Adding domain user: no exact match error

I set up MDS on a standalone Windows Server 2012 box. Now we want to let other users access the web app via the Excel Add-in from their laptops on the company domain. We NAT'ed the web server and can access it using the local server username and password.

We then joined the server to the domain, but when I try to add domain users (ourdomain.local\jdoe) I get a "No exact match was found for ____" error.

Is this due to the fact that the MDS Services account is a local user? I can get a domain MDS User Account set up, but will it have the correct roles?

Thanks.

BTW, the .local predates me.