Ryu Theme Older Posts Tab Not Showing Correctly

I am currently using the Ryu theme for my blog. When I first started using it, there were two arrows at the end of every post pointing left and right, each showing the title of the previous or next post (this was great!). I would prefer to have only one post showing at a time. When the arrows were clicked, it would refresh the whole page to show just the next or prev post.

Now the arrows are gone, and the only option is a square that says ‘view older posts’. When clicked it just loads an older post under the post I’m currently viewing.

How do I get the arrows back that allow me to click forward and backward through the posts? I’m stumped.

My site is: https://www.bbmishmash.com

Thank you!