VST plug-ins not showing up on Mac

[ihf]

I tried installing a set of VST audio plug-ins from here http://mda.smartelectronix.com/vst/mda_vst_ub.zip into the /Library/Audio/Plug-ins/VST folder but they do not show up in OBS. Why would that be?
What is a good source of compatible audio plug-ins for OBS on the Mac? (I am running MacOS 14.6 and OBS v25.0.8.