How Come My Garmin Nuvi Wont Pick Up A Signal?

Silly question, but do you have the antenna up? If you’re holding it in your hand with the antenna down, it won’t pick up a signal.
Otherwise, it may take as long a 3 minutes to acquire satellite signals, especially if you’re near tall buildings which interfere with the signal. Get out in the open and stop moving to give the unti time to capture a signal.