Verify that the buildings main unit and spare units are all on the same subnet.
On the main unit, click File
Verify that the third option in the File menu says “Switch Company File to Single Mode“. If it says “Switch Company File to Multi User Mode“, then click that option.
If the above two options have been done then…
Switch the main unit to Single Mode
Then switch the main unit back to Multi User Mode
If #4 didn’t work, try shutting down the spares, then performing #4, then during the spares back on.