This opne is resolved. I needed to add to my congig.ini file:
excerpt_allowed_tags = “a,img,abbr,blockquote,b,cite,pre,code,em,label,i,p,span,strong,ul,ol,li,script,object,embed”
Config.ini? There is no file with such name in WordPress. You will not see a YouTube video in the home page because the_excerpt(); eliminates all HTML tags other than <p>.
If you want to show the video on your home page, edit your theme’s index.php or home.php and find the_excerpt(); then change it to the_content();.
Make sure the specific youtube clip allows embedding.