Hi there and welcome
Is the Garmin still functioning at all? Even when disconnected from the computer?
Please let me know.
This is usually an issue with the Firmware, so I would first like you to do this please.
Remove the charger from the Garmin and hold the power button to off for 35 seconds.
Release, then connect the charger and try to turn on the Garmin.
Let me know the results please