I seem to be having the same issue. Win7 here, Vizio E50C, wired connection, Mullvad VPN.
I used iperf3 to monitor my forward port and looks like it is hitting it but not able to connect right. I made a quick video to show that PMS thinks it has access for a split second (message turns green) and then fails again… you can also see the port gets hit in the video.
