I'm desperate...

I can't find a way to use the unlocked maps available for download (CN North America NT 2017.30 for example)

I tried to downgrade the firmware.

I tried the Universal Firmware Patcher for Protected Garmin Devices, but i can't get to pre-boot mode (none of the methods works and entering the hidden pages by pressing and holding the battery symbol and then connecting the USB lead gets me to pre-boot for 2 seconds, then it disconnects and the updater is unable to work properly).

I even tried gimgunlock-0.03+MapSigPatch applied to the already unlocked maps.

Please help!!!