... they don't see the notifications because they're knocked off the top of their screen by Snapchat notifications.
They both have Android phones. For Whatsapp/Gmail, there will be one on-screen notification, no matter how many messages they get. But for Snapchat they seem to get a notification for every 'snap' so they're all lined up at the top of the screen and quickly take up all the space, relegating other notifications to a less visible off-screen list (accessed by swiping).
I've searched to see if it's possible to limit the Snapchat notifications to one only, but the results so far have only said how to completely turn notifications off.
Are there any Snapchat users out there with a solution to this?