AC66U port forwarding doesn't work

Hi, I used to be able to forward ports fine, but recently after several firmware upgrades and a change of dynamic ip to the device that the port forwarding was intended for, it seems as though I can no longer forward any ports at all several months later. I tested the ports by running the application they are intended for (nba 2k16)and also with portchecker.co

I've tried:

- factory reset
- updating firmware
- updating to merlin firmware
- opening ports in device's firewall + windows...

AC66U port forwarding doesn't work