2003 BMW Z4 car won't start

Check all the fuses. Go inside the E-box and look for a isolated fuse holder with 5 two legged fuses inside a "trapped" plastic non user friendly box. Open it, I give you permission, look for blown fuses. If not then you possibly have a bad throttle motor/engine wiring harness issue, there is a factory bulletin on this. Or collateral damage from the serpentine belt excursion. I also recommend timely inspections to possibly preclude these issues from recurring.