My device was fully charged this morning and prompted me to update the software, which I did. Then I put the device to sleep and 30 minutes later when I got ready to go for a ride it wouldn't power back on. I plugged it back in and went for a ride without it. Came home and the device still won't turn on. I've tried holding the on button for 20 or 30 seconds and tried holding the down button at the same time (something recommended for a similar issue with a 520) but no luck. Any suggestions? Thanks.