Apologies for the delay in responding. I have followed the above steps, we had performed those prior to my initial posting.
This particular office has 3 users who work in QB. All are up-to-date on the latest release. None of the 3 are hosting multi-user mode. At some point, they are just unable to enter multi-user mode. The time varies, but after running QuickBooks Database Server Manager they are able to work in that mode. This will last anywhere from 2 hours to 2 days before it just suddenly stops working and we have to run QB DSM again. Very frustrating. This is a brand new server and was not happening on the old server, so it's possible that something was not migrated or set up correctly, but it was basically done as many other server migrations we have done in the past.
