** WARNING - Not certain the following is correct. Problems are resolved, but specific cause and cure are unknown. **
Multiuser debugging in Pervasive Database. I didn't find this information too easily on Pervasives website, so I'll put my interpretations here. There is a very high probability that this is all rubbish, and I've miss interpreted the documentation and pervasive's website. Anyway, here are my notes, perhaps others will find it useful.
Pervasive has three modes: client/server. workgroup. workstation.
The files and installation for workgroup and workstation are EXACTLY the same. The database server will default to Workstation mode which allows ONE connection. Think of it as a local database that isn't shared. To "upgrade" to Workgroup mode, which will allow other machines (which can be in workstation mode) to share the database, you need to do the license disk upgrade thing. (Which has been done on the server). [Edit: I think this is incorrect, workgroup mode always allows 3 connections UNLESS it is set (in the PCC) to NOT allow remote connections in the Server properties]
Net result: to let multiple people use the db at once, you MUST allow the server to be the "master" machine. See the .LOC file in the database files folder. If it doesn't have your Server's name, only one person can get in to Accpac (or your other Pervasive apps)!
To set the server as the master machine, exit PERVASIVE on all machines except the server, then restart pervasive and accpac. (Or just reboot...)
For some reason, TCP/IP would not work for me in Workgroup mode. If TCPIP doesn't work, it will default to NetBios mode. NetBios did work, so if you have similar problems, try it, it will eliminate some sources of error. Unfortunately, I think ODBC required TCP/IP so you may need to continue debugging. FWIW, the Pervasive TCPIP port is 3351. As it turns out, something else was taking up that port on the server (Crystal Pageserver service was using 10 or so ports, including 3351, see linked Scribble below). Once the port was freed and the pervasive engine reloaded ALL was finally good. Accpac and ODBC and multiple logins.
Use the Pervasive System Analyser. It works pretty well to test communication settings.