The ‘Too many workstations in use’ is an error presented by Omnis when more than the licenced number of users is trying to open an Omnis application or datafile. So it is possible that you do not have the required number of licences.
However, there are other possibile causes associated with file sharing across the network.
When sharing an Omnis datafile (not SQL), the datafile is opened across the network by each user.
As each user opens the datafile, a lock is placed on one byte in the header record of that file.
File servers changed a whle back and stopped supporting the ‘byte range protocol’ of old.
Omnis introduced something called the Omnis Data Bridge to resolve that. It’s not something I’ve ever had to use as I’ve been building SQL systems for years.
In summary, you might just need to contact Omnis Software and purchase a multi-user serial number to allow multiple users to run this application simultaneously. However, you might need someone experienced in Omnis programming to set up the ODB for you. Either way, I would look for an Omnis developer to support this application going forwards and consider getting trained in Omnis if you want to do this yourself.