[Unity] Open the Unity project and report an error manager 'TagManager' is Null

The project that was just completed yesterday has been checked without any problems. When I opened it this morning, an error was reported directly. The content of the error report is as follows:

pointer to object of manager 'TagManager' is Null(table index 2)

After Baidu for a long time, I found a similar one:

Automatic packaging error Fatal Error! GetManagerFromContext: pointer to object of manager 'MonoManager' is NULL (table_ChrisZhao520's blog-CSDN blog introduction When Jenkins is automatically packaged, it will always fail to package and report an error Fatal Error! GetManagerFromContext: pointer to object of manager 'MonoManager' is NULL (table index 5). It is suspected that it is caused by a bug in the low version of UDP in Unity IAP. The following introduces the temporary solution steps and the final solution steps after self-test (completed, but not yet integrated into the master). Temporary Solution step 1. Close Unity and UnityHub1.1 including UnityHub in the lower right corner of the menu bar https://blog.csdn.net/z741092665/article/details/120761063 but this is index5 and mine is 2, so I am considering it what is the problem.

After struggling for a long time, a colleague told me that if you look at the log file, there is nothing there.

I tried for a long time and found that the resource files are all right, other files cannot recognize the format, and they cannot be opened even after reinstalling Unity.

Finally, after deleting the Library and Temp files, reopen it, unzip it again, and finally. . . .

opened. . . It's just that the materials of a few objects are missing, and there is nothing wrong with the project

This problem is a bit inexplicable. It is suspected that it is caused by too many cache files after opening it before. But the specific reason is not clear, and the error cannot be reproduced, but the problem is solved.