Seemed simple enough from the Microsoft documentation. Fill in the forms, add the user, set the credentials. All done, no errors. Proceed to add the External Data Type in SharePoint, add the data connection and squat. Login failed. Ugh.
The BI stack:
SSAS Tabular Model Database
Admin role added Sharepoint 2010 front end
Needs data driven Lists or embedded, data connected Excel
Asked the system the administrator to restart IIS in hopes that SharePoint needs it in order to update it's configs. Now, we wait...