Your antenna has probably failed. I'd doubt that it has become unplugged, because it would give you an 'antenna' error on your display, not a 'no signal' error. If you can't seem to acquire a signal, then your antenna has probably failed. I don't know how many miles you have, but it should be covered under the 3/36000 warranty if that still applies to your vehicle. If you're out of warranty, the tuner should be under the passenger front seat. You will see 2 cables plugged into the unit, one large cable, and one tiny cable with a black 90 degree angle bend right at the plug. You should be able to go to any car audio shop and buy a sirius antenna (about $40-50 MSRP at the most, you can find them online for about $20) and just replace that cable. It isn't that difficult to do, however I've done one or two

If you take your time you should be able to make it happen, or the car audio shop where you buy your antenna from should be able to do it for youpretty reasonably. I'd try to warrantee it through your dealer first if at all possible