Hi Alan M,
That ticket has been marked as SEV1 and a tech has sent you details for a remote session. You mention message: "Server update is in progress. Logons prohibited during server update"
Please try this:
Check for a file called updaterunning.txt in the kaseya\webpages\install directory on your server - if present, delete it.
I suggest you update the ticket or call 877-926-0001, option #2, quote the ticket number and ask to be put through to the technician.
Regards
Amado, Kaseya Support