When I try to design a page with an upload and a progress bar (for showing some processing progress), these two elements are not shown.
The DOM shows only
Basically, this happens when you don’t have any View that uses an Upload or Progress Bar directly. Either you add the Upload using reflection, or other generic methods.
in the github it says this will be fixed in 14.1
If you need a fix now, for me it worked when I declared a field of that type in any view with a @Route. That field doesn’t have to be used.