Beginner: Material on an Actor BP is missing in the Level.

Once I place an Object converted to Blueprint Actor in my Level, some Materials doesn´t show up. Why? Do I miss something? ( first I imported a Model with Datasmith, then put Materials on it, setup the LODs and finaly put everything in a Actor BP. I removed the original and put the Actor in the scene).

Well first better fix these warning,.
Open your material carpaint and checked this:

If that fix your issue, that mean your model has some polygons that have been flipped.