Why aren't dots showing up on iMessage from some people?

[iMore Question]

Dots not showing up on IMessage from SOME people

Hi; Our son had his battery changed in his IPhone 5. Everything is working well but suddenly he doesn't receive the "dots" from SOME people when they're sending him an IMessage. And for some it works fine. My guess would be in the settings of some of the people he communicates with and THEIR settings. But it doesn't work with MY IPhone 5 and has for a couple of years. Please help. We've set and reset every setting we possibly can...