Port Forwarding does not work - DMZ does

so, like SO many others here, port forwarding does not work.

yes, i have tried for TWO DAYS to read all of the articles on the xfinity website so PLEASE do not link it and tell me to read the port forwarding instructions.

i have forwarded ports before .... for years and know what i am doing.

unfortunately, i have the xfi gateway for unlimited data so i cannot do this in the admin console and HAVE to use the xfinity app.

i have completely removed the NAS - forgotten using the app and reconnected it.

ALL of the settings are correct in the NAS.

i have DHCP set -> not static IP on both devices (NAS and gateway).

i have selected the device and forwarded the port. it is NOT on the list of blocked ports.

i am unable to connect.

when i enable DMZ on the device (NAS) then i can connect using my said port.

please fix this! it is insanely annoying.