I guess you mean last three digits and that will be service code 7- SRO (static return to off).
That basically means that you have tried to operate the machine without your hands and feet in place.

I've suggested that you check the hand sensors.
If you did, you should check the feet sensors (micro switches on the floor board). When you step on them with both feet the strobe lights should start blinking (beware! Users are sometimes annoyed by them so they disconnect them). Try to check this...

Regards!