I’ve tried the standard 2022 theme as well as the one I normally use and the same thing happens which makes it look like the EME plugin is stripping/overwriting the title value from the shortcode somehow.
Your test site is not responding, but I installed the plugin and added this to an event:
[su_box title=”Important” box_color=”#e6000c”] Some information.[/su_box]
and it works as expected (with the title). Theme I tried: twentyone. In twentytwo it also works but the title is rendered white so it seems invisible by default (because the background is white too), maybe that’s the problem in your case too.