TFSConfig Identities listed all TFS accounts and all but one matched Windows.
How do I fix the lone user account where the Match is False?
While this may not be relevant, I add it to the post in case it provides any additional clues. I tried to reapply the user in the Application Tier Console Users list and it failed. The log stated the account is also an orphaned SQL Server Login. I assume that makes sense if the SID is mismatched, though.