Have you checked your message app to make sure the notification setting "app icon badges" is set to on?
I meant for the individual message app, as the badge icon option can be turned off for certain apps while still allowing for others.
quickest way to check.
Long press on the message app icon,
when a pop up shows, tap the little "i" in a circle (top right of the pop up)
Then tap the "notifications" option at the top of the screen.
You should be taken to a screen of notification toggles" on this screen you can check if the message app itself has the "app icon badges" activated
"The screenshot you show is the kind of universal app icon badges" which just allows the badges in general....but you can set them all individually via the apps notification settings using the same procedure I mentioned.
And now I'm stumped
Have you tried switching to the other message app ? on my device I have google messages and samsung messages.
I find the google one less hassle
other than making sure your message app isn't in battery saving mode, or in sleep mode via the battery care settings, I am not sure what else to mention
Well I was missing texts from a friend over xmas, I thought I would try the pre installed google messages as it doesn't wake your screen every text...which I don't like having it wake all the time.
I found all the missing texts within the google app once I set it to default...it just works better than samsungs app unfortunately