We've reached out to our teams internally and have this statement;
ASUS does not officially sell any Tencent-branded ROG Phone II with so called "International ROM" or "Global firmware".
We cannot guarantee the functionality of this combination , if you are facing any type of issues - please turn to your reseller where you bought this device - as this is is not a combination we are selling.
It is very likely that the "WW ROM" being installed on these Tencent-branded Chinese versions is the culprit causing issues - but this is very much unsupported from Asus side - and not a combination that we officially sell anywhere..
You may try to flash back the CN firmware and see if that restores functionality to the camera - but of course that brings about its own set of issues. Our recommendation is that you bring this issue back to the resellers who sold you this type of combination.