Just following up on this: After spending 1h with support on this, I was advised to go to a store and replace my modem. Needless to say, I did and the issue persists even with a new(er) modem...
I am having the exact same issue. IP shown by the Valerie modem is a private IP (10.X.Y.Z) and none of the Port Forwarding rules are working.Thank you for your help.
