I get this occasionally on my phone and feel its a glitch.
Actually even tho it says failed on my phone its actually gone and been recieved.
That or I hit resend or as you start a new text message to reply.
Annoying glitch I admit @DJH
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "