I to have the same problem Trying to convert to TH
Stuck at garmin screen only.
I cannot seem to go to Mass storage or even Pre Boot?
Maybe someone can help?
I do not have a GUPDATE file on the device i deleted that before.
I used rgn tool to load the TH gdc and then replace the original boot from my device.
I then flashed it usong update.exe but then it stuck again in the boot and reboot.
What am i doing wrong. My devie is a 1490 KP1
2. Touch left top side of the screen and keep touching it.
3. Push the power button and the garmin logo will show.
4. insert the USB cable
5. Drag your original RGN file to updater.exe
now you should be able to select USB in updater.exe and be able to start flashing.
you can now release the left top side of the screen.. this worked for me
I upload it to the .system folder and after restart it starts flashing but same result stuck again to garmin screen.
Now reflashing the original firmware in preboot mode and everything back to normal what am I doing wrong?