Viewport Matcap is black

Sorry for my English, I use the Google translator.
I have a problem. Mattsap works fine on all objects, but on object does not work correctly. On tank treads matkap is not working properly.
Watch the video

So where is your blend file to look at rather than just some video that doesn’t tell all the story.

Is that track an array along a curve ? If so are you selecting the curve or the track. If you select the curve it obviously won’t show up as a matcap

Also please use the appropriate forum for support questions. You may find your problem important but what is this to do with blender discussion ?

Moved to Support / Basics & Interface

how add file?


how add file?

my example