How do I get rid of a red triangle with an! In the middle

[AC Question]

I have one phone number I am trying to text to and each time I hit send a few minutes goes by and a red triangle with an exclamation mark comes up and it says retry and I have not been able to text this person how do I get rid of this red triangle or how do I actually connect with my text

 

[onnad]

What phone do you have? Have you tried closing the messaging app and reopening with re sending the text? Another thing you could try is to deleted the message with the triangle and retype it and see if it will go though.