Sometimes Instagram blocks certain users/devices. Hard to tell why.
Start with a clean install of iGrann: Follow These Steps
Then try what other users have done to solve the issue:
login to www.instagram.com from your devices browser and change something in your profile (Ex: your bio, but NOT the username or password) and then log out. Usually, this validates your account and the need for verification goes away.
I only opened and tried chatting (DM) and there you go, there was no more message popping up.