Fwiw, I believe that happened bc you dared to comment on a post that was since removed by a mod from a magazine hosted on another instance. Now, that whole post is "gone", so Notifications cannot reach it, but it is "not gone" in the sense that Notifications cannot properly realize that it's gone. And it has poisoned your whole notifications system, to the point that you cannot even read other notifications from other posts.
The good news is that it only affects one "page" of your Notifications, so as you continue to operate, it will eventually fall behind to page 2, and thereby still prevent you from seeing any Notification from that whole entire page, but from then on at least you will get new notifications from page 1. Until it happens again, ofc, and the cycle continues. I have ceased recommending anyone to come to KBin as a result of this extremely frustrating bug, along with the other highly frustrating ones like constantly logging you out, and barely being able to type out a comment on mobile. Hopefully it gets better.:-|