You should only get 1 headlamp wash for every cycle of the key, so basically it only works the 1st time you use the washers, every time after that only the windshield washers will work. Once you shut the car off and restart it again the 1st wash will again be headlamps and windshield. You may or may not have already been aware of this but I thought I would mention it to help you with your testing.
If they are not working I would check for leaks in the lines. Im not sure if there is a separate pump for headlamp washers but look and see if there is and if so see if it is working.