Hi everyone. I cannot update my phone. manually either. update failure appears. with asus updater no updates appear to me either. attached firware of my rog phone 2.
Unfortunately I can't offer any official help for you, that configuration is not supported. More information on why can be found here.
With that being said, I can leave you the link for the download and an FAQ on how to manually update the phone. If you already followed these steps (it sounds like you might have) then sadly that's all I can do.