My project started out years ago. Now using VS 2019.

Whilst I can right-click and add event handlers (since it uses a new VS wizard), and I can right-click the class and add generic variables (since it uses a new VS wizard) I can't display class wizard any more:

I have tried cleaning the project and tried renaming my folder.

It refuses to display and shows that message:

Value does not fall within the expected range.

The other error message that shows is:

The parameter is incorrect. (Exception from HRESULT: 0x80070075 (E_INVALIDARG))

This means it is very hard for me to attach new variables to new controls on dialog resources.

I have researched this issue and can't find a solution that works for my 2019 MFC project.

Update

I tried using the Visual Studio Installer and Repair and that did not resolve the issue.