youtube in main menu

hi
I have installed the theme correctly but i have some problemes with post.
When i post somthing including a youtube link, the video dosnt show up on main menu. i can only see a gray box. But when i click on that gray box i can see the video in the page not in the main menu. You cant test it here https://www.paykazadi.com

I have also tried all methods both with embed, htmlcode, youtube link, youtube sharing link etc. is this a php or css problem?

thanks for your help and sorry for my bad english.