I recently upgraded to 2.1.2 and are now experiencing issues with my VST-plugins.
Audacity lists them under plugins, but as disabled and it doesn’t help if I enable them.
Examples include Voxengo Elephant and IK Multimedia TRacks processors.
I have been using them regularly for some time now though, before I upgraded.
I tried freshly downloaded Voxengo Elephant and IK Multimedia T-RackS CS Brickwall Limiter on Windows 10 in 2.1.2 and they enabled and appeared to run OK to me.
You could try reinstalling them (only the VST 32-bit versions will work with Audacity).
Perhaps also, exit Audacity, delete pluginregistry.cfg in Audacity’s folder for application data then use Effect > Add / Remove Plug-ins again to enable the plugins.