Sticky posts not showing on slider

I’ve been using the Pinboard slider for years now until few months ago all new sticky posts doesn’t appear on my slider. I don’t know if it’s because of the recent update to wordpress. I’m using the latest version of WordPress and Pinboard theme as of the time of this writing.
I have existing sticky posts in my slider which when I try to uncheck the sticky post checkbox, update the post, then check the sticky posts checkbox again, it will also not show on the slider anymore.