Port forwarding rule is not showing

My husband created a port forward on his PC when port forwarding was still done on the Xfinity Gateway (we now have an Xfi Gateway), but it is no longer appearing in the app. I just tried to create the port forward using my PC, and I got an error that the port is already assigned to my husband's PC, and to remove the rule or delete the port forward to his PC in order to proceed, but it's not displaying in the list of port forwards to delete or remove. We've rebooted our gateway, both of our PCs are connected to the home network, the gateway is not in Bridge Mode, and none of this has resulted in the existing port forwarding rule displaying under Network > Advanced Options > Port Forwarding. Any help is greatly appreciated!