Ah, good to know…
Have you checked this box in the Plugin Manager?
Studio/VST-Plugin Manager down at the very bottom
Please try to able/disable it to rule out any VST2s first. As the VST2 standard does not know a dedicated installation folder, VST2 plugin installers usually let the user select an installation path. But VST2 plugins can also have a fixed installation path predefined by the manufacturer. In this case, only the documentation can tell you where to find the plug-in…