Indeed, I'm able to see all my existing VST3 plugins, but strangely, I can't spot the newly installed ones after the last few updates—probably around 3 or 4 builds ago. I didn't notice this immediately.
When I initially posted, I believed I had the very latest build installed. Yet, upon revisiting today after reading your post, I discovered version 7.3.3502 available. I promptly installed it, but there was no change in recognizing the new plugins.
Mainly UADx (native), which I'm thrilled to see they're finally porting to native support.
I've taken the liberty of attaching two screenshots for reference. One showcases what I see inside Vienna, while the other exhibits a partial list (which, amusingly, is longer than the window can handle 🤣).
Nevertheless, it's not confined to just Universal Audio. If my memory serves me well, it's also affecting the new free Waves plugins that were recently released on Black Friday, as well as other Plugin Alliance stuff, and some more.
Hope this helps!