Update!
Installed a Tazer mini today, and before I made any changes, I paired and rebooted the system, then two sleep cycles and the instant mpg came back. So I’m guessing a glitch in the factory software.
I spent a few hours at the dealership this morning with the same issue and they didn’t have a clue. Said give us some time to do some research and they would be in touch. I won’t hold my breath.
My 22 did the same with less than 200 miles on it and no matter what I tried it never came back. off, on, reset to default, disconnected the battery too. I actually lost a few of my icons and then had to do a soft reboot to get them back and still nothing. I guess it’s a trip to the dealership.