Only Cub Cadets - RZT-SX46 won't start

I have a RZT-SX46 that was working, then died while cutting grass. Model is 17RWCBYN010 date of manufacture is 08/21, SN 1H26MH10050. It has a MTD679cc EFI engine. It has about 321 hours

I have replaced the battery, hour meter, magnetic key, solenoid, ignition coils, and spark plugs. The engine will turn over, so I don't think it is one of the safety switches preventing it from starting. I checked the spark plugs and they are firing.
I removed the fuel hose to the throttle body and cranked the engine, getting a lot of gas into the throttle body. The butterfly valve in the throttle body is open. Could one of the electrical connections on the throttle body be bad? How is the fuel distributed once it enters the throttle body? How is the fuel/air mix handled with a EFI?

thanks