Sounds like your Hills clothesline has been with you for quite a while. Here are two ideas that will reset the mechanism inside the clothesline:
If the head is at its lowest point, you may try rotating the handle clockwise and push the head up at the same time.
If the head is at its highest point you may try to rotate the handle anti-clockwise and pull the head down at the same time.
Still stuck? Could be time to buy a Replacement Winding gear assembly from our spare parts store.