EssentialPIM Pro Network stopped working

[nathMS]

I upgraded from EPIM Pro to Pro Network. PC1 holds the db and firebird, EPIM on PC1 connects as SYSDBA to db.
PC2 connects as a user. Firewall questions were fixed and everything worked well.
Then I changed Internet provider and got a new dsl modem from the new provider.
Since then the above configuration no longer works. PC2 can no longer access db. I get the message that host failed to reply within a given timeframe. I tried opening all ports for both epim and firebird, without success. Voth firewalls on both PCs are now completely off. Hence this is not a firewall problem.
And of course, I tried uninstalling, reinstalling all three programs (2 epims and 1 firebird), restarting both PCs... etc...
What could the problem be? Can you help?
I can copy the db from pc1 to pc2 and open it there, but then what is the point of having the network version?

TIA.

[Max]

It is some network issue. Make sure both machines are inside one Network.