Can't connect new laptop to existing Plex setup on another computer

[OttoKerner]

Do you have a FIOS router or use a provider whose routers have a similar advanced firewall inbuilt?

[FIOS] Internet Connected but no access to Internet while PMS is running

I did discover that if I turn off FiOS Home Network Protection from the FiOS Mobile App that PMS works fine and Internet connection is good. Contacting FiOS Support about this is leading nowhere.

Otherwise see if this can help: Plex install fix for Windows Server (Claim issue)