To be a bit more specific, there is a plate that covers the tool carousel motor. This plate is about a foot square. Inside are the two proximity switches. one is the tool count and one is tool number one.
The entire tool changer moves to and from the spindle. This flexes the cables for these switches and they can break.
Just because the switch may change state does not mean the control sees this.That wire may be broken.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)