On my s10 plus at night with do not disturb on but set to allow favourites through I get the ring tone but screen don't open up with green answer button always did on s8 plus has an option changed. Try these steps: Go to Settings > Sound & Notification > App Notifications. If it starts getting warm, give your phone a break. I deleted the messenger data at no avail.
You can try these steps here to see if they actually help: * make I am able to show incoming call notification and full screen (when phone is in locked state).
Messenger incoming call not showing android not sure what causing it but On my Note 5, after each call, i get a popup that reads "just call with" and then their contact name.