Welcome to the forum!
As others have said, we need some more info.
If they made the thing fail, they need to fix it. If they won't fix it, there are avenues that you can take to make them fix it.
But, if you want us to try and fathom out what it could be, we'll need to know a bit more about what is happening. Does the engine turn over at all? If not, maybe the battery has had it, or the starter/solenoid or maybe even just a fuse to the solenoid. Let's start by telling us what the car DOES do when you turn the key - instrument lights, clicks or noises, engine turning over?
It's possible that in messing with the chip, they've done some damage to the electrics. Some chips connect to the fuel pump, the fuel rail sensor, throttle and the ECU. An incompetent pulling at wires could have disconnected anything. Let's hope it's not too bad!
