I think these will eventually drop off in time, but you could try deleting:
connections.xml file from C:\Users\<user>\AppData\Local\Graphisoft\ConnectionInfo\14.0.0,
TeamworkInfo_v2.xml file from C:\Users\<user>\AppData\Roaming\Graphisoft.
I don't know exactly where they are on Mac. Make sure all instances of AC14 are closed first and the next time they access the BIM Server, the users will just need to enter their username and password again.
I don't guarantee it will work, so just try it on one machine first. The process is pretty harmless, but if you want to back up those files somehwere first, go ahead. I do this quite regularly whenever we we run into similar connection issues.
Please let us know how you get on.
Cheers,
Link.