Make sure the fuse assembly did not fall out of the 12 v plug. Normal driving produces vibration, which causes things with screw assemblies to fall apart. I found the fuse, spring and positive contact in the bottom of the bag where I keep the Garmin. When I reassembled the power plug, the Garmin now works fine.
Thanks for the help. The solution worked the first time I tried. J
I had the same problem recently... What I did was open the front casing and hit the reset button under the cover, then it turned on while plugged into the car adapter.
Usually answered in minutes!