did you manually add it to the list in the plug in manager and then scan it?
Also..... this is an AUDIO plug so be sure you are trying to add it to an audio track fx bin or it will not show up in the list.
be sure to register it with IK so it will function in full operational mode and not revert to demo mode after it times out....
Doesn't MC6 come with Amplitube or am I thinking of something else?