The nylon cable has broken, most likely where it hooks on to the spool it winds around when the antenna retracts. You aren't likely to be able to do anything with it short of breaking the mast off without removing the whole unit from the car.
Most of these are repairable. They sell kits with a new mast and the nylon cord attached. You disassemble the mechanism, remove the old broken pieces, and thread the new one in. Last one I did took about 1/2 hr.
drc
