Sounds like the driver is not engaging in the driven tool and after two or three tries it alarms out. Hold a block of wood or something against the tooling nut to create drag and see if the coupling drops in and the mill spindle gets up to speed in mdi mode. If it snaps in and you still get the alarm you have a proximity switch problem. If it works, your bearings in the tooling are getting too loose and you'll have to figure a way out to make the tool drag a bit. We put alemite fittings in the tooling and over packed it with grease to create the drag. This was on a 1st version multiplex. They have refined it a lot since those days. We worked with slowing down the speed of the coupling extension by installing a regulator in line to the cylinder so it wouldn't push as hard against the driver thus slip a little and let the driver line up and drop in. The sensors are under the center aluminum center cover and should have led indicators on them when they are made.