Insert Gallery Button not Working

I’m working on a new Intranet site and decided to use the Slider Gallery from the plugin. I was able to edit settings and create a gallery for my post. I can even get to the screen that lets me select the gallery. However, when I click insert nothing happens. I tried searching older posts and have yet to see a response on what the issue could be.

I currently have WP 5.4.2 installed and I’m using the Twenty Twenty theme.