Must be the season. My antenna stopped going up and down too. We bought a new mast, but when we compared it to the one we took out we realized that the nylon part was not as long on the old one, meaning that the nylon cord was broken off inside the power antenna casing. We had to get open the case of the antenna and remove the remaining piece.
If the mast needs to be replaced you unscrew the cap that holds the mast to the motor, turn on the radio and the whole nylon cord will come right out.
If the new cord is longer than the old cord you need to get access to the motor which is not easy to get to.
You need to pry out about 7 of those black fasteners, the top of the wheel well, remove 2 of the cargo net hooks and take apart most of the back end.
Then you dismount the antenna assembly from the car with 2 10mm nuts,
Then open the assembly by removing 6 phillips screws, and remove the remaining cord. A big painfull job, but not really all that difficult.
Then you can feed the new cord into the assembly and install.
Vicky