Check the spark, I bet it's gone again......

Stupid immobiliser system will have you chasing your tail. Sometimes it cuts injectors & spark, sometimes just injectors. grrrr.

Yes the immobiliser is probably your problem, have you got a spare key to try. They are the most common fault.

Alternatively, try tow starting, some Hyundai's have a fail-safe, in the event of vehicle speed during running, it defaults to mobilised.