For some reason Akai MPC is not always registering the VST folders. Please make sure these two folders are listed in the preferences:
- for 32 bit VST support on windows: C:Program Files (x86)Common FilesSteinbergVST2
- for 64 bit VST support on windows: C:Program FilesCommon FilesSteinbergVST2
Make sure to press the rescan button.