If you have only a new internet connection I am not sure this will impact MP. But what is your set-up.
Do you have TV client and Server on the one computer?
If not what is your network set-up, you have a router? Do you use dynamic IPs on your network? When you get the new internet connection (ISP Internet Service Provider), is this the first time you have re-started the router. If so the re-start may have changed the alloacted IPs.
You can generally allocate fixed IPs for devices (computers) in the router. So if you know the IP that the server was then you can set the router to force this. You will then need to re-start the network connect on the PC (possible easiest to reboot).
If this is all off track post some more details of your set-up and the exact problem.