Resolved MonoBehaviour is red but no error in console How to debug?

I do not know how to fix this bug or debug it.
If I open Visual Studio, the MonoBehaviour is underlined in red.
There are no errors in the console.
I am using 2020.3.14f LTS with the last updated pachages.

SOLUTION
This is odd; I do not understand why but
If I copy my project and open it using the Unity Hub, the problem is fixed.

 

This may help you with intellisense and possibly other Visual Studio integration problems:

https://forum.unity.com/threads/intellisense-not-working-with-visual-studio-fix.836599/

Also, try update the VSCode package inside of Unity: Window -> Package Manager -> Search for Visual Studio Code Editor -> Press the Update button

Also, this: https://forum.unity.com/threads/no-suggestions-in-vscode.955197/#post-6227874

 

I have tried with no success.

• Unity, go to Edit < Preferences < External Tools (left part of the Window) Visual Studio 2019
  
• Project > Reimport All
• Updating VSCode package: Window > Package Manager > Visual Studio Code Editor
• And also Visual Studio Editor

I did not understand well this process:
https://forum.unity.com/threads/no-suggestions-in-vscode.955197/#post-6227874

I left this project because of this error. But now I'm trying to fix it. Hours trying to find the origin: 16hs

SOLUTION
This is odd; I do not understand why but
If I copy my project and open it using the Unity Hub, the problem is fixed.

Any Clue?
I make a compare and these are some different files plus a mygame.sln

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