"Property Not Allowed" in angular.json error in Visual Studio CODE for Angular CLI version 9.1.1

The schema is case sensitive. If you wish to fix:

Goto: ./node_modules/@angular/cli/lib/config/schema.json

At around line 27 you should find:

 "projects": {
      "type": "object",
      "patternProperties": {
        "^(?:@[a-z0-9-~][a-z0-9-._~]*\/)?[a-z0-9-~][a-z0-9-._~]*$": {
          "$ref": "#/definitions/project"
        }
      },

Change the regex pattern to allow Uppercase project names:

"^(?:@[a-zA-Z0-9-~][a-zA-Z0-9-._~]*\/)?[a-zA-Z0-9-~][a-zA-Z0-9-._~]*$"

The error was gone when change project name and all other occurrences for it in "angular.json" to lowercase letters. no need to create another project or any other stuff.

It is working fine on stackblitz, sometimes VS code behaves strangely. Try closing VS code and opening again, that helps most of the times in these cases

working example https://stackblitz.com/edit/angular-dhtbbh