Xfinity App cannot port forward

Hello, I have been trying to set up a port forward to my device and am at a total loss -- I've followed all the guides, restarted everything multiple times, and nothing works. I open the Xfinity App and navigate to add a Port Forward, yet each and every time I get the same message:

We're Having Some Trouble
Please try again.If the problem persists, check backlater.

Please help! I have successfully set up port forwarding before, I cannot understand what's wrong this time around!