Check the batterys both in the fob and in the car
The fob can work with a dead fob battery in it when inserted in the slot.
The battery is a common cr2032 I think, you can find it any drug store for
about 3 bucks. Or you can get 5 of them for 2 bucks of ebay.
Sounds like the Fob battery is dead.
Comfort Access Battery's are not rechargeable.