Did it happen after you tried to do an update, etc
I bought the GPS about 18 months ago and have been using it frequently. This issue only arose today. The power was low so charged it up and when I turned it on it came on with the 'test screen' I didnt try to do any update or anything like that
*Master resetting the device will erase all history in the device and reset the device to factory default.
To master reset your device:
Power the device OFF
Press and hold on the top-left corner of the display
Power the device back on while continue to press on the display
Press on Yes when the Reset device settings to factory defaults? message appears
Thanks Andy however it didnt work. The Reset to Factory default screen appears briefly then the screen goes a bit darker and then it switches to the test screen
So you will have to send it to Garmin and they will charge you a flat rate to repair the unit for you.
Please click here : LINK on instructions about how to send it for repair.