This error can occur, when you have moved or deleted the package. UPM package content isn’t stored as files in the Unity project. Only a reference to the tarball file is.
For instance, if you have imported the VisionLib package to your project from your download directory, and you remove it there, you get such an error.
The location of the tarball file is important and moving or deleting it will break the dependencies of your Unity project. To prevent this from happening, save the package to the
Packages folder of your project and import it from that location. This will result in a relative path in your
Read more on this and installing UPM packages in the documentation.