Hi sreed27,
as you correctly guessed you have resolved a jQuery conflict.
this is 99% times the source of the problems you might encounter with the default Lighbox style of simplest gallery.
I do not a have an always-working method to fix jQuery conflicts in all situation, your procedure seems to having changed the oder of loading of the javascripts so it gets fixed.
Stay tuned though, as on https://www.simplestgallery.com I will post soon a few tutorials about how to solve fairly common jQuery issues (eg. “$() is not a function” error) and a gallery style which is not using jQuery at all, just to solve the problem at the very basic level!
Can I mark this as resolved?