I was about to make a new topic for this, but I found this one via Google.
The problems still exists. It’s a really simply fix, though, so maybe somebody will see this and take a minute to fix it.
It looks like there are two menus (done by Wayfinder?), and the last element of the first one has this:
Simply remove that class from it and the divider should show up.
I’m on a 22" screen and the resolution definitely has nothing to do with it.
EDIT: Nevermind. It looks like it’s going to take more than that to fix it.