Suddenly cannot access file from two computers at once
We have QB Enterprise 18 set up with one host computer and two user computers. Only one of the latter two is able to access our company file at a time, while the other will either show a message about checking their firewall or it will show error codes -6190 and -816. However, if one user logs out, the other is always able to log in without issue. The host can log in at the same time as one of the users, but never both users at once. We are in multi-user mode, and QuickBooks has worked fine with everyone logged in until now. How should we go about troubleshooting this?