Filemaker clients can access remote files but FileMaker go cannot. These setups previously worked. What can be blocking fm go?

Well I have at least discovered what the problem is.  My FM Pro clients and FM Go can connect to the Server from outside my local network, but not from within it.  Would anyone know how I can get my router to accept internal communications?  And not just external ones. 

Are you using the same url inside as outside to connect to FMS? If so does the the url internally resolve to the internal IP address of the FM server or the external? Can you connect using the ip address?

I agree with the @OlgerDiekstra. If you use the IP address of the server it will probably work.

Getting your router to resolve the FQDN to the local IP address is different for different routers. Most routers will have a DNS Lookup section in the Configuration console, and you can just add the FQDN and IP address pair and it should work out.