Case:
This is happening to me in Unity 5.4.3.f1 from a Windows 7 64-bit project going to a Mac (El Capitan 10.11.6), using git repositories for transfer. Several critical objects are "Missing Prefab" in the scene hierarchy.
I tried deleting the Library folder and re-opening the project, same result.
"For anyone getting this error after recreating a project from a git repository - make sure the repo has all its .meta files checked in or prefab references can be lost. Contact the creator of the project (or tap yourself on the shoulder if you did it) and tell them to check everything into the repo, then resync your project and watch the errors fade away! Otherwise see the other answers."
Sure enough, my .ignore file had a *.meta filter for some reason (it was auto generated by my git client).
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Solution 02:
One computer used blender for some files. The other computer doesn't have blender, then unity don't recognize theses files and can't make prefab who use them.
You have to install blender on the new computer, delete your project and reimport all.
--possible solution(s)--
Taken from https://forum.unity.com/threads/missing-prefabs-with-freshly-downloaded-project-windows.411721/
Case: This is happening to me in Unity 5.4.3.f1 from a Windows 7 64-bit project going to a Mac (El Capitan 10.11.6), using git repositories for transfer. Several critical objects are "Missing Prefab" in the scene hierarchy. I tried deleting the Library folder and re-opening the project, same result.
Solution 01: Came across this answer at http://answers.unity3d.com/questions/278326/missing-prefab.html
"For anyone getting this error after recreating a project from a git repository - make sure the repo has all its .meta files checked in or prefab references can be lost. Contact the creator of the project (or tap yourself on the shoulder if you did it) and tell them to check everything into the repo, then resync your project and watch the errors fade away! Otherwise see the other answers."
Sure enough, my .ignore file had a *.meta filter for some reason (it was auto generated by my git client).
--
Solution 02:
One computer used blender for some files. The other computer doesn't have blender, then unity don't recognize theses files and can't make prefab who use them.
You have to install blender on the new computer, delete your project and reimport all.