Hello,
I had the described problems with my FritzBox 6360 Cable after installation of uRADMonitor either.
I tried several different LAN-ports, the monitor was visible in homenet and all required ports to the internet were open. Anyway, the uRADMonitor was not able to send packets.
Suddenly it worked fine without any further action. I do not know the the reason for the problems up to now.
I only can recommend to try several different ports and to restart your router after changing ports.
Good luck.
Joachim