You would need to reset your device so that it can read satellite signals again..I have done this and it works
1) Swtich off your device
2) Keep pressing the bottom right of the screen and swtich on the device
3) The GPS will pop up a message saying 'Erase all user data'
4) choose Yes
5) make sure you leave your garmin for 45min in open area where clear satellite reception is there..The garmin will learn the satellite signals