Hi,
you’ve posted to the VST Transit forum. Your problem sounds like an general Cubase problem. Anyway …
Be sure that your VST3-Plug-In is located in one of the following folders
/Library/Audio/Plug-Ins/VST3
/Users/YourUserName/Library/Audio/Plug-Ins/VST3
You have a VST2 Plug-In, then it should be here
/Library/Audio/Plug-Ins/VST
/Users/YourUserName/Library/Audio/Plug-Ins/VST
If the Plug-In is still not visible on Cubase? Check the Bit Type of your Plug-In. Maybe you have a 32 Bit Plug-In, but you are running Cubase in 64 Bit mode. That will not work …
Have a nice day,
Michael.