Similar question
I recall a very similar question once. We suggested that there's not enough pressure to close the diaphragms on all the valves at once so none of them are closing. If you have a flow control, which is right in the middle of the valve, try turning those off one at a time to see if you can build enough pressure to close the diaphragms. It worked for that guy.
Good luck!
If I can't fix it, it's broken!