Does anyone know how to open The Mpc Vst Plugin in cubase 15???
Talking about the MPC64? It’s a VST2 plugin, so you first have to enable VST2 support in Studio→VST Plug-in Manager.

Cubase 15 Doesn’t support Vst 2 anymore
Depends. On Native Silicon mac that’s correct. Otherwise Cubase does still support VST2.
The Enable VST 2" button doesn’t even show
Then you must be on Mac silicon running native. If you run in rosetta you can run vst2 but your performance may suffer.