Hi,
The reason is, that there is a custom shortcode just above the blog post section, but the parent (container) element is hidden. Because of that results shortcode, the results are mitigated there, but the parent is hidden, so they are not visible. This is how it looks like when I change it via the debugger: https://i.imgur.com/wOQw36Z.jpg
If that section is not in use, I recommend removing it, or using a different search instance shortcode there instead (you can make a copy of the original one if you want).