We'd like to help. Could you check with your subs, is this happening for desktop, mobile or email notifications (or all of the above)? Also, is this happening with *all* notifications or just certain types? Appreciate the additional info.
Hmm, could you ask your subs to double check your bell settings for the channel and make sure they've opted-in to receive all notifications and not just "occassional". After that, make sure the device settings are turned on: https://goo.gl/UCRcbp . Let us know.