My METAMASK QR Scanner is Inoperative on my IPhone 12. Hence I am unable to sync with desktop. What happens when I click the box is a momentary black screen pops up then nothing. My other QR Scanner app works ok for other uses.
Welcome to the MetaMask Community @Kevin!! 
What version of the MetaMask app are you using? Are you using the scanner when you first download the app?
Hello and Thanks bharmon 0/, I am using MetaMask V2.1.0(608). I am only trying to use the scanner (so far) to sync with my desktop MetaMask which is version 9.3.0. Also of possible interest for troubleshooting is that on this IPhone 12 Pro I have AT&T with its VPN currently enabled. When I click the scanner button it just flashes a black screen momentarily and reverts back. I was trying to sync with desktop because there’s an obvious disagree with the amounts of ETH I have from mobile to desktop. Also I did try a reset of the desktop with no apparent changes.
Thanks
Kevin
The QR code sync feature only works with a fresh download of the MetaMask mobile app. Once you’ve restored your wallet, the sync function does not work. What discrepancies are you seeing between your mobile app and extension? Is it the fiat value of ETH or actual token balance?