YoutubeGallery Theme Not Set
Since Youtube Gallery 3.x you need to select not Gallery but Video List and Theme
In Menu Item and Module select Video List and Theme
Where 1 is Video List ID and 2 is Theme ID
JoomlaBoat.com is not affiliated with or endorsed by the Joomla! Project or Open Source Matters.
The Joomla! name and logo is used under a limited license granted by Open Source Matters
the trademark holder in the United States and other countries.