according to the simple image gallery pro feature list -- www.joomlaworks.net/content/view/25/42/
the galleria template is supposed to work like a slideshow:
"...and the JavaScript enhanced "Galleria" which transforms your gallery to a slideshow."

I'm using this template, but it doesn't auto-advance the slides as one would expect from a slideshow. i'm not getting any js errors in the console, so it doesn't appear anything is broken. but it doesn't work as advertised.

Did you check Galleria at the demo site?
There is no rotation option in this plugin...

then you shouldn't market it as a slideshow.
if you say it's a slideshow, people expect it to act like a slideshow -- and auto-advance through the slides

by way of comparison -- when you market your frontpage slideshow extension -- you don't even explicitly state that it will auto-advance -- because that's assumed by the extension name -- the very fact that its called a slideshow.

your promotion of this extension is very misleading.

This is why it is called SIG PRO Gallery and not slideshow. However, some pop ups in SIG PRO work like slideshows!

quote from your site:

"...and the JavaScript enhanced "Galleria" which transforms your gallery to a slideshow."

you indicate that template works like a slideshow. so I expected it to work like a slideshow.
you should remove that, since it does not, in fact, work like a slideshow.

This means that it have the look of a slideshow.
That is why you should check the link to our demo site.