Perhaps, you could go outside with a clear access to an open sky with no tall trees or buildings around, in order for the device to 'see' the satellites. You could also make sure that the WAAS/EGNOS and GPS settings are enabled (set to ON by going to Main Menu > Configuration > GPS Setting).
Another thing that you could try is to do a Cold Start. You can do this by pressing the POWER, OK, and DOWN buttons at the same time. Then, go to Main Menu > Test Mode > GPS Test > Cold Start to reset the GPS data from the device.