Hello, my name is***** to Justanswer! Give me just a few minutes to look up some specifics, I'm working on this now.
It sounds like it went into calibration mode on its own. I want you to plug it into your computer in order to fix it. The computer program does most of the work for you.
If you do not already have Garmin Express on your computer, click here and install the program. There is an update button which will automatically restore the software that runs the Garmin, and it will also update your maps so you'll be completely up to date.
Let me know if that doesn't solve the problem.