What *exactly* does "then it stopped" mean?
What specifically happened between the time it worked and the time it "stopped"?
What *exactly* does "just wouldn't work" mean?
What did the shop say, exactly, in detail, and did it work for them?
If it didn't work for them, then there's not much reason to pay them for the parts or work?
Did they keep your old parts, or give them back to you, or reinstall them? (because if they replaced the parts and it didn't fix it, they aren't the problem, but they might help you find out what is *really* wrong--without them, you are stuck trying to figure out what the shop could have done wrong with the new parts, or if the new parts are even any good, or if they are even compatible with your system, etc).
The less you tell us the less we can help.
The quicker you provide as much specific exact detail as possible, the quicker we can make relevant suggestions.