XM radio displays antanae not found
it seems a lot of vehicles like ford and chevy have a problem with getting moister in the antenna on the roof and causing a no signal. this video might help. it is for ford but might help you too. or someone with a ford vehicle with this problem.
How to fix “No Signal” issue Ford Satellite Radio - YouTube
Also, if you have been to a car wash recently, make sure the roof antenna is not loose or broken.