should be fixed eventually when the lists are fixed
https://www.mangago.me/home/mangatopic/21080691/?page=1
"the issue is on the technical side of things like the login token. Even if youre only using two devices (or on your specific case, even if your logged in correctly), if that token gets corrupted, expired, or desynced from mangago's servers, the site can temporarily lose track of which manga and notifications belong to your account."
Ah, but you can also re-add your previously read comics to your reading list. And voila, you'll receive another update if the comic uploads a new chapter. But I personally choose to wait patiently, because I'm afraid if I mess with my reading list the notes I left on each comic I read will disappear, I hope not.

i haven’t gotten notifications for updates in like a week now. usually it updates maybe twice a day or two but it hasn’t shown any updates when u click the bell. but when i look up comics i am reading and i see that they have updated. someone plz help (´°ω°`)