Why doesn't unity find EventSystems and UI?

Question

Unity

After installing UnityEngine.Monetization, the project was automatically changed. I open the solution in VS 2017 Community. Now there is not one project in the solution, but 3: MyProject, MyProject.Editor, MyProject.Plugins. Now the unit swears at the line using UnityEngine.EventSystems; (the type or namespace name 'EventSystems' does not exist in the namespace 'UnityEngine'). In addition, there were errors in the line "GetComponent ()" (could not find Image) and a bunch of the same errors. What is the problem here?

Answer 1

I have exactly the same problem: VS didn't see both .UI and Events. Today, for some unknown reason, I saw Events. Today added Unity.Notifications - also does not see it. Although everything works correctly. Moreover, VS Code (Package Visual Studio Code Editor 1.2.0) - sees everything perfectly. But she has her own jambs)
Unity 2019.3.7f1, VS 2017. That is, like a crutch - VS Code.