Not 100% sure , but if your car has drum brakes on the rear then the chances are your self adjusters have seized up, they work on a ratchet principal and should adjust every time the handbrake is applied.
Release the handbrake, chock the front wheels so the car can't move, then jack up each rear wheel in turn , and remove the brake drum, you will see the adjuster between the brake shoes, remove and free it up, a trace of coppaslip to lubricate.
Manually click the adjuster round, until the drum will just go back on, do the same on other side, and your handbrake will work, you will also find a difference, in your brakes generally, as a lot of lost travel will have been removed in adjusting the handbrake.