Probably am being U.
But I have a couple of friends, one lives down the road, who on several occasions don't open messages from me. I can see that they were active on Watsapp but didn't open my message. Sometimes for a long time. Or don't reply at all and just message me if they want something after a while.
One of these friends I saw in the street last week. I'd messaged her a few weeks ago (left unopened). Very very friendly in person, invited me round and was generally lovely.
I then messaged to say nice to see her and should we try the new coffee shop that's opened round the corner sometime. No reply, not even opened. She's on her phone all the time. Surely she'd have time to open a message in a week.