You can try also this. Not sure whether it helps, but trying it won't harm anything:
My Garmin forerunner was locked on the 'transferring data' screen and this worked for me without losing any data:
For the 910XT you might need to try a master reset. It's a little tricky and requires some dexterity. Good instructional video here:
You can try also this. Not sure whether it helps, but trying it won't harm anything:
If you can access the watch folders through the USB cable, check also the activities folder, if it is not overfilled with files. The reason of the frozen state could be perhaps due to full storage. You can delete older activites to free up some space.
My Garmin, which has worked reliably for years. None of these ideas below has worked. I wonder if it's a coincidence that others have had the same problem recently.
For the 910XT you might need to try a master reset. It's a little tricky and requires some dexterity. Good instructional video here:
Thank you so much, I got it going! For a few happy moments I thought I could justify getting an Apple watch or new Garmin ... but for better or worse the 910XT seems to be soldiering on!