Whenever I send a message from my phone it won't say delivered

I am trying to contact a friend from school but I'm running into some message problems. Whenever I send a message from my phone it won't say delivered on my phone but it will on my computer (vice versa too, sending a message from my computer results in delivered status from phone but not computer).

Is there something to recipient could have done to cause this? I didn't think I was blocked because it was delivering on at least one device, but when my other friend texted them it delivered from their phone immediately so I don't think my friends service is out. Could they have me personally on Do Not Disturb? I just need to know if they are actually getting my messages or not.

[Re-Titled by Moderator]