"Some projects had trouble loading: check output for more details" in VS Code

So, I was switching to VS Code because VS was wasting my space. So I installed the extensions OminiSharp, IntelliSense, Debugger for Unity and Unity Tools, and setup Unity 2020 with it.

As soon as I open the project,

And in the output it is written this:

 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\UnityEngine.UI.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\UnityEngine.TestRunner.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.Mathematics.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.2D.Animation.Triangle.Runtime.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.Timeline.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\UnityEngine.Monetization.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.TextMeshPro.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.2D.Animation.Runtime.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\UnityEngine.Advertisements.csproj
 [fail]: OmniSharp.MSBuild.ProjectManager
         Attempted to update project that is not loaded: d:\Development\Unity\Projects\Parkour Ball\Unity.Postprocessing.Runtime.csproj

There is a lot more fails here.

Now IntelliSense stopped working. It does not give me real errors. It gives syntax errors for this:

 using UnityEngine;
 
 public class HelloWorld : MonoBehaviour {
     void Start() {
         Debug.Log("Hello, World!");
     }
 }

And on Visual Studio, there is nothing.

On the setup, I got into Edit > Preferences > External Tools and set it from devenv.exe to Visual Studio Code, and regenerated all project files.

What did I do wrong?