Check your program. That message is saying that you commanded the turret to index while the milling tool was commanded to run. You did not say what machine you have but a lot of Okuma live tool turrets use one motor. There is a shift fork controlled by a piston that engages the motor to the live tool gear or the turret index gear. There are prox switches that monitor the shift position. If it was a problem with the piston, shift fork, or switches it would generate a different alarm than what you have. You have a program alarm. Check out the M-codes in your program just before you use a "t" command.