Just a thought, to get the watch to sync, you could try putting the fixed fit file in the \GARMIN\NEWFILES folder on your watch, then sync. Normally that would tell the watch that there is something new that needs to sync.
tried that .. found the following file in \NEWFILES .. moved it to ACTIVITY and tried to sync .. got the SYNC error. I'm not sure if this is pre-sync copy of the 2021-01-11 file or not.
