Instagram has another folder that could be full of unread messages

Open up the Instagram app. In the top right-hand corner, you’ll find the normal inbox – but opening that will show the “message requests” option in bright blue if you’ve got any messages from strangers that you haven’t yet opened. If you don’t have any messages in the other inbox then nothing will show up. Instagram’s messaging feature is probably not as used as Facebook's one, but you never know what - or who - might be lurking in there. That's of course if you can even still bear to look at Instagram since its contentious logo redesign.