Sage 100 Workstation Synchronization doesn't finish.

Recently completed a Sage 2022 Advanced upgrade. On one computer out of about 20, the synchronization starts but then disappears with the logon prompt never appearing. I have removed anti virus from the computer, checked that the user has sufficient permissions to the C:\Sage folder where the client is installed and to the \\servername\SAGE\MAS90 folder. 

No idea what to try next. Any suggestions?

Thanks