Ah, I've forgotten that 37xx can't be seen in Garmin USB mode in the battery menu.
Let's try another magic.
Unpack the Garmin folder to the root of an SD card. [Only registered and activated users can see links. ]
Insert the SD card, turn on the device, wait until it reboots and prints "LOADER", then wait 10 minutes.
Then send SD:/Garmin/Updater/1101/update.log to me in private.