First thing is to determine if the washer is served by its own pump or only the front one. Either way, the pump(s) is electrically operated.
Yours is probably operated by the same stalk switch on the steering coumn. One way works the front one and another the rear. Turn on the key and have someone check to see if they hear the rear motor running when you figure out which switch runs it. If the motor is running, then it may be the small hole where the fluid sprays out is clogged. (It's amazing how much algae grows in the fluid). A small pin can clear it. If you can gain access to the area where the tubing from the pump attaches to the spray device, you can disconnect the tubing to see if fluid is running... that will at least, confirm the pump is working.
If no motor noise is heard, but two switches are detected, the motor is probably shot and will need replacing... and that's a whole other story...
Best of luck!