I'm also having the issue with the slider not working. My site is currently in maintenance mode (though I have tried deactivating this to see if this fixed the slider issue, but it didn't).
The posts are tagged with garage-doors (also tried featured), I've also updated the tag name in the theme customisation section
They are marked as sticky
I do not have the Jetpack plugin
The theme is the latest version
The posts show up in grid view, but not when I change to slider.
It seemed to work when I only had one post, but as I added more, it broke.