Unpack the downloaded .zip file, run abdiagtool.exe as administrator, and click the Find and Delete Ablebits Products button:
Run abdiagtool.exe with standard privileges and click the Find and Delete Ablebits Products button again:
Important! Run the abdiagtool.exe file twice: as administrator and then with standard privileges. As a result, after each launch you'll see one of these messages:
Download your edition of Ultimate Suite for Excel from the Latest versions page.
Install Ultimate Suite for Excel again.
Remove the Ablebits Diagnostic Tool from your machine.