If it's the first power up of the device or it's not been switched on for a good while/moved a considerable distance since last acquiring satellites, it may take a very long time to get a fix. Have a go at placing it in a position with a decent sky view and just leaving it, on mains power overnight if necessary. Worth a go as it may not be faulty, just confused.
Personally, I rate Garmin stuff and haven't had a faulty unit yet, even post drops from heights, being frozen, immersed in seawater, used as hammers... you get the picture. Also find I can get a fix from a cold start on one marine unit within about 30 seconds of firing it up even having crossed oceans since it last knew where it was, although this is unusual compared to most which suffer as above.
If the above fails, remember, a year's warranty means nowt. Consumer law is based on what the reasonable man might expect, ie. more than a year's service. Go back to the retailer and have it out with them for a replacement.