Plex player issue on a network 10.10.10.x

Hi From Greece.
We have a plex pass account on geobikas@libver.gr
I have my plex server on a Virtual Machine with windows 7 with no issue.
Yesterday I tried to give access to our plex collections to library users through free wifi in our library.

Since Yesterday I was working with addresses like 192.168.1.x and now on freewifi network there are 10.10.10.x
All devices have access to the server and can browse to files but……..the player is now working with the following message.
When I change to 192.168.1.x everything is working well. Is there some port or whatever that I have to check out?
The server is having a static ip on both cases and cliends have addresses with dhcp.