Cannot forward port 80 on RAX45

I cannot forward port 80 on my Netgear Nighthawk RAX45.

I get an error saying: Port conflict with other service.

No other service is using port 80.

Searching seems to indicate this is an error often caused by having Remote Management enabled. To my knowledge I do not have remote management enabled, not that I can check as the Remote Management option has been removed from my router, so if it is enabled I would not be able to disable it anyway.

I have disabled Anywhere Access through the Nighthawk app.

Firmware version: V1.0.5.106_2.0.70

Any advice on how to enable forwarding port 80 at this point will be appreciated.