Why do messages sent have a red triangle with explanation point on only one contact?

[AC Question]

messages sent have red triangle with explanation point on only one contact

the texts are showing that they have sent. this is only on one contact

 

[B. Diddy]

Re: messages sent have red triangle with explanation point on only one contact

Welcome to Android Central! Are you sending a group text? Or do you have a number of sent texts to different contacts, and there's one contact that it never successfully sends to? Make sure that contact's number is correct.