My notif has a glitch

Idk if anyone of you experienced it, but a manhwa in my reading list got updated this morning, but it was not in the notification later that day. I doubled checked it and indeed it has an update, it is still in my reading list, but did not appear in my notification. I somehow already experience it few weeks now that I haven't read a 1 or 2 previous chapters during an update but I just brush it off saying I may have missed them while browsing my notification.