The messaging could be improved here.
In case in helps someone else, check if the data host has Windows updates pending!
This is a recurring issue.My client's company data files reside on a central Windows computer and the user opens the company with Sage 50 (2017) running on her computer. The error upon attempting to open is the "firewall" error message. However, nothing had changed on her system such that the firewall which allowed it the day before would be blocking it now, several Sage programs are "allowed" in the firewall just as before, and turning off the firewall completely still doesn't work. Rebooting her computer didn't resolve it.
On the other computer hosting the database, connection manager was running without issue. Stopping and restarting the service just to be sure didn't help.The solution was to check the status of the Windows updates on the data hosting computer - allow them to install and reboot if required.
You see, if program and data are on the same computer, you will see the message: "Sage 50 has detected a Windows update on this computer" in this instance. Because she wasn't opening the company directly on the other computer, this correct message isn't seen.
The "firewall" message obtained upon failure to open the company when data file is not local (on same computer), should include an additional hint to the effect of:If you are attempting to open company data file residing on a remote computer, that other computer may have pending Windows updates to complete.