Unity Recorder "the type or namespace could not be found"

Hello, I don’t usually work on Unity, but now I’m trying to update the Unity version for a project created about a few years ago.

Currently, I updated its version to 2019.4.29f1, and I have 62 compiler errors and all of them reside under the Assets/Unity Recorder/Editor. Since the first couple errors were the same as this thread, which is

‘UIElements’ does not exist in the namespace ‘UnityEngine.Experimental’

So I was able to solve it by changing the

using UnityEngine.Experimental.UIElements;


using UnityEngine.UIElements;

however, I cannot solve the rest of the errors like,

Assets/Unity Recorder/Editor/Timeline/RecorderClip.cs(6,19): error CS0234: The type or namespace name 'Timeline' does not exist in the namespace 'UnityEngine'
Assets/Unity Recorder/Editor/Sources/RecorderItem.cs(10,26): error CS0246: The type or namespace name 'VisualElement' could not be found
Assets/Unity Recorder/Editor/Sources/RecorderItem.cs(16,18): error CS0246: The type or namespace name 'Toggle' could not be found 

So my questions are

  1. This sort of errors happen because I upgraded the Unity version? (if not what causes those errors, and why only under the Unity Recorder happens)
  2. What could be a way to solve this “type or namespace name XYZ could not be found” error?

@harada_unity861 Yes, it happened because of version upgrade, Unity Recorder does not come into the Assets folder anymore it goes into Packages folder so you should try deleting the Assets/Unity Recorder folder and reinstall the latest Package from Package Manager. Hope this solves your problem.