Hi, similar issue here too.
Just upgraded to a new Android 12 phone and Android 12 tablet. Backed up all data to cloud and installed FIF onto tablet, loaded the backup, all ok with logs/routes etc. but no circuits as they were in a remote country (Barbados!) as previously advised. Went to import my own circuits (.kml's) as usual but navigating to my 'Circuits' folder storage the kml list is not visible. The kml's in the folder open in other phone gps apps (GPS Essentials for instance), so I think they are ok. With the new phone however I did the direct transfer update by cable from the old Android 7 phone to the Android 12 and no problems, everything shows up, previously installed circuits as well. Then tried to add a new circuit to the phone as an exercise and got the same result as with the tablet, no listing kml's visible in my 'Circuits' folder in FIF. So tried an airspace/pattern export from the phone to send to the tablet but that failed to complete. It just looks like a kml visibility issue in FIF.
I've attached a typical kml file I made in GE for for Old Sarum in the UK if that will help..
Si