I have just created new photo galleries and although I have setup, and tried, both a "Pop-up" window and new windows when the site/page is published clicking on the thumbnail does nothing. i.e. pictures do not open. Have tried this only on local publish because I don't want to update the site unless it's working, but on 2 different machines the result is the same.

I am sure there's something silly that I am missing but what?

Help Please.
Malcolm