Virtual instuments_no parameters available

Hello.

When I try to use virtual instruments, a window pops up and says “No Parameters Available”. And I don’t hear any sound of virtual instruments.
I think this is because I have moved the VST related folders here and there, when I was trying to set up a new virtual instrument set called Spitfire.
But Spitfire had an error, so I deleted it. Now I am trying to switch to the new virtual instruments that I have downloaded, but it’s not working.
The new instruments are located here:
Local Disk (C:) > Program files > Steinberg > Cubase 12 > VST2

I look forward to your comments.
Thanks in advance.

Usually, you get those kind of dialog when the plugin in question is not accessible for Cubase, ie it is no in the respective plugin folders anymore (you should have gotten a warning window with entries like “The plugin … cound not be found…” on project load).
Your screenshot shows “Halion Sonic” though, that is a Steinberg Plugin, and it is not even VST2, it is a VST3 plugin. In case you damaged or delete that folder, I would suggest re-installing Cubase and additional products like Halion Sonic.
C:\Program Files\Steinberg\Cubase 12\VST2 is not a common Folder for plugins!
VST3 plugins should be located in c:\program files\Common Files\VST3
VST2 plugins can be located anywhere if you set the respective path in the plugin manager, but preferably should stay in one of the default paths of Cubase:
image

Hello.

Following your advice, I have re-installed Cubase. I have also relocated VST3 plugins in c:\program files\Common Files\VST3.

Unfortunately it doesn’t work yet, although I do see my virtual instruments in Steinberg Library Manager as below. I don’t understand why it’s not working.

I look forward to your further advice.
Thanks in advance.