Hi,
What is the model number of the Magellan GPS?
Most Magellan units have a “reset” pinhole somewhere either on the side or the bottom edge of the device..
Try inserting a pin into the hole and check if you feel a pushbutton when you ''gently'' press down.
If you do, hold it operated for a few seconds and then release and then check if the device has been reset and is functioning correctly.