Sticky posts disappearing

Hi,

I am using the Vina theme for my site https://fourleggedworld.com and I am having an issue with making a sticky post.

I want to make a post I wrote sticky so it stays in the top section, but whenever I choose the “make sticky” option, the post disappears. It doesn’t show anywhere. I tested it on several different posts and the same thing happens every time.

Any ideas how to fix this?

Thanks so much,
Vicki