What turret?
Barafuldi TOE 60/80, or Denfords own one?

The Barafuldi won't work correctly if the three phase has been connected wrong, as it's relying on a 3 phase motor to rotate things the correct direction (note that the spindle runs through a VFD, so will still run the correct direction regardless of phase order, it's only the turret that won't work).
If it is a Barafuldi, try swapping two of the phases around, and indexing it again.

Without dismantling a Barfuldi turret, you can't manually unlock or lock it. If it has failed to lock, you can sometimes spin them by hand, but it relies on a locking pin being engaged and the motor reversing direction to re-engage the hirth (IIRC) coupling to lock it, and the motor running without the lock pin engaged to unlock it. If you're interested in how it works, there is a technical manual for them on the Denford forum somewhere, but it probably won't help you solve the problem of why the controller failed to index it (unless a sensor has failed, but that's not likely).