Block frontend styles/JS not working

I installed & activated the plugin and added a Images Slider block, with “open lightbox” set. It shows up in the editor as a slider but on the frontend it displays only as a stack of images (no slider controls, links, or lightbox functionality).

When I came back to the post to edit the block again, I can’t edit the slider
block but it does display as a functioning slider (only in the editor, not on the frontend).

This is in a custom theme, if that makes a difference.