This is a tricky one to fix.
Make sure your Z axis pulse in coder is working. Make sure the tool arm is not stuck on the spindle nose. If so you will have to pick the Z up a bit.
You will have to go into your parameters and also trick the tool change position proximity switches that the tool change operation is in its home state.
(1) On my machine I have to change address (467) from value 0 to value 1. The NC will alarm thatís OK.
(2) Stick a steel object in where the proximity switch is located in the tool change mechanics. The LED on the switch should turn on when the switch is closed.
(3) Above the tool change ARM there will be another proximity switch you will need another steel object to close that switch as well. Use something long donít want to lose a finger.
(4) Put the machine in Jog mode and jog the arm home.