I have the same problem and it still hasn't improved...
I think its not really update notifications issues, but all reading list have been deleted..so all the mangas u listed as reading, and u been getting notification disappeared. They tried bringing back but only the ones u rated came back as "read".
I used to get 11-12 new chaps notifications twice a day but now only getting one or two...
TTwTT whyyyy
Is this happening to anyone else? I bookmark a lot of manga so I usually get 2 to 3 update waves a day with new chapters. Since 2 weeks ago I have gotten no notifications but i know that new chapters have been added because I went into the manga to find out. Any fixes for this weird issue??