in the test application (latest version 64 bit), selecting plugin preference from the edit menu does not show any preference window (it does nothing). Is this by normal ? where do you set the plugin folder ?
How do you start it? Have you read where plug-ins need to be installed (Log In - Steinberg Developer Help) ?
I start it as a normal windows app from the start menu.
I installed some free vst plugins in all 3 locations: app/vst3, common/files/VST3 x86 and 64.
No plugins are detected 
Started as an administrator, same issue …
Solved. there was an issue with the vst3 plugin…