Assettimestamp Errors
Symptoms:
Did you just open the project and get assettimestamp errors, or errors with Extension not registered (VR) or InitializeUnityExtensions that look like these screenshots? There's an easy fix to these.
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The Fix:
Simply close Unity, open the project folder and delete the Library folder. Then reopen the project in Unity. Unity will recreate the library and the errors will be resolved.
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Select the Game scene, open it, and Play.
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Still getting errors?
When you open the Game scene, do you see a blank screen or get errors about UI buttons? Make sure you've already installed the necessary plug-ins (read Installation Instructions here
Also, check this link for more details: https://issuetracker.unity3d.com/issues/unityengine-dot-ui-dot-dll-is-in-timestamps-but-is-not-known-in-guidmapper-dot-dot-dot-1
Updated less than a minute ago