So, I guess you're using Safari; I'll have to give instructions as I see things on Monterey.
In Safari preferences, under Advanced, make sure "Show Develop menu in menu bar" is checked. Then, in the Develop menu that appears in your menu bar, select "Show Javascript Console". If you refresh the page with the console showing, you might see errors and they might lead you to some answers. Also, look in the tab next to "Console", labeled "Network". Perhaps that will show errors indicating some resources were not found.
I'm really just grasping at straws. I know that when I'm doing development, when my pages don't load completely, that's the first place I check.
Or, the page is loading fine, and it's just not trying to load the toolbar. As
@maternidad suggested, maybe it's just a setting on the site. The setting could be remembered by the browser rather than the server, so each browser could have it set differently.