Material is not visible in Render

[murathankalender]

Hello,
After opening my assembly file, I enter the Render section. I add material as appearance, but the material I added is not visible. This is not for every piece. I had this problem in sigma profile part. I had no such problems yesterday. How can I solve this problem.
Thank you.

[wmhazzard]

You need to be more specific. Please attach an f3d file of your work and specify what appearance you want.