Unable to create UI objects in Unity project

I’m sure it’s a simple fix, but I just can’t figure it out. I can add UI elements to new projects, but not to this one.
86419-noui.png

just restart your project and it will work

Hi. I was actually just looking at a similar issue today, but in 5.6.0. If this reproduces for you could you please submit a bug report?

Edit: Also worth asking, what is the full path of your Unity editor install?