Unity missing reference at Library/PackageCache/[email protected]

Here are a few suggestions for tracking down the issue. Hard to tell what is missing.

• close unity and delete Library and obj folders. Then open Unity again. It will re-sync those folders.
• disable collaborate from services window in 2019- or window/collaborate in 2020+ and see if the issue gets resolved.

I just updated from 2019.x to 2020.3.x and ran into this problem. I tried clearing my package cache and ensuring the Collaborate service was disabled (Window -> General -> Services), but neither worked.

What fixed it for me was removing the "Version Control" package (a "built in" package, I believe. Check your filter in package manager!). I was never using Collaborate or Plastic SCM, just git, so I don't know why this would cause a problem from a simple upgrade. 🙄