I recommend reaching out to the developers regarding this.
? What you expect
It is supposed to have writing on there. In that case it supposed to say "Somebody is at the door". It said it with my S8 but not my new S10+
Having the same issue with all of my notifications, still no fix. They show up if I switch to night mode but go back to all white if I turn it off.
White on white or light; I am having the same problem with themes, a couple of links from emails to unsubscribe and pictures I use for wallpaper.