Bug Everything that's coming from the package manager is not working

When I installed Unity on my computer, I noticed right away shaders don't work as well as the collab button was missing. I reinstalled several times, made sure I did everything correctly, but nothing worked. Later on, I discovered that it's not just the URP/HDRP ad Collab that's not working, but everything I try to install from the package manager. The things I install are indeed installed, as I can see them in my library folder as well as in the manifest, but for some reason, Unity does not recognize them at all, as if they do not exist.

I haven't seen anything like it online and I have no idea what to do.
If anyone has ever encountered that and/or have any ideas on how to solve it, please address me in this forum.

I appreciate all the comments.

**Edit**
Note that everything that I download and import from the asset store DOES work, as well as all the other features Unity has. The ONLY things that don't work are all the packages I install via the package manager.