My boyfriend never reads his texts

Basically, my boyfriend is awful at reading his messages. I’ll text him in the morning, and I won’t get a response til late that afternoon. I get it when he has work or prior plans, but this’ll happen on a weekend when he’s doing nothing. I will see the notification pop up on his phone, hear the little ding, and he won’t check it. It makes me so frustrated because it will make me miss out on stuff that he wanted me to come to. For example, he and I were invited to dinner the other day with one of his friends and I didn’t know if I’d be able to go. I told him that a while back, but then plans changed and I let him know the morning of (it wasn’t a fancy dinner. It was at like Waffle House) and asked if I’d still be ok to come. He said yes and then I asked where it was. I never got an answer. Like at all. He’s such a good boyfriend besides this. I love him more than anything and he does try to make up for his mistakes. It’s just this thing that gets on my nerves. So, what should I do?