I think many of us are using reverse proxies, and opening port 443 (https) and maybe port 80 (http).

It’s a shot in the dark, but are you running a vpn on your phone? That might mess things up.

Manager is the highest. (I think there are only two tiers anyway.)

There is something uniquely wrong with your setup; this is not a general google router issue. Which is good news, you don’t need a new router. The next obvious step (for me) would be to wipe the data for the Home app on the phone and re-set it up. If that doesn’t resolve it, you might consider resetting the router itself to factory, though that could be more annoying.

Port management works on mine for creating forwarded ports. Could it be that you don’t have the proper access to edit these settings?

If it matters, my home app is version 3.2.1.7 (Found under Settings -> Support)