I think that has been happening more since the app upgrade. I spoke to VC about it, they said they knew there were issues with the new app. Most of the issues have been resolved now but this intermittent failure of alerts is still happening, and like you I’m frequently checking. I normally find that the alerts have appeared in notifications once I open the app, so I haven’t been checking each item daily (heavens, what a pain!) but I might double check that now!
My problem is that I get so many favorited/wishlist alerts on my items (probably 25+ a day) that the list of notifications on the site gets very jumbled. I wish I could disable those notifications. I did finally see that I could disable the notification when someone follows me. Another thing that makes it so confusing is that the timing seems to be delayed by many hours, I will get a notification and immediately go to the page and it says it was from “yesterday”. I’m not sure if the notifications are sent out immediatley and they are using a different time zone as the set time, or if they are really delayed by up to half a day?