Asset Store Issue: "All Assets From This Package Are Already In Your Project"

I've been trying to import some particles into my project, but every time I try to import it just gives me an error telling me it's already in my project. I tried importing some other random assets to see what works and what doesn't and it's seemingly random.
If it helps, the package I'm trying to import is the Unity Particle Pack 5.x

 

What makes you think it isn't already in your project? Go to where the asset should place them, and verify they for sure aren't there.

 

Unless this particular package places them in a really weird location, they are definitely not already in my project.

 

Create a new blank project, attempt to add that asset to the new project. It should then tell you exactly where it would place the files from the asset. Cancel that, open the original project, and go to exactly where it installs those files and see what is there.

According to what the editor is telling you, you will find the asset is already where it should be.

 

Created a new project and attempted to import the assets. Again, it told me they were already in the project. I don't think it's a matter of me not being able to find them.

 

I am having the same issue basically. Assets>Import Package> Custom Package.
"All Assets From This Package Are Already In Your Project"
This didn't start happening until I was updated to the 2019 version. I tried rolling back to the 2018.3.6 I was on and that didn't work.

 

Same problem here, but sofar only with the Raw Mocap Data for Mecanim package.

 

I'm running into this same issue right now with ArchViz Pro

 

Has anyone solved it?
I have the same problem too.
I even tried on a new empty project, but nothing changes.
"All Assets From This Package Are Already In Your Project"