I get text notifications from everyone except one person. How do I get the notification to sound for this person?

Open the Messages app. Locate the thread with the name of the person that you are referring to. Is there an icon, on the right , that looks like a BELL with a SLASH through it? If YES, then that indicates that the sound notifications for that person have been silenced. If this is the case, then you can TOUCH that Message thread and then SLIDE it to the LEFT. This will display options to Silence Sound (BELL) and Delete thread (TRASH CAN). Tap on the Sound option (BELL) and that will reinstate the sound notifications for this one person.

Axel F.

Open the Message app on your iPhone and in the main Message window, slide the message thread from that person to the left and tap the bell-shaped icon. If the bell has a line through it, notifications for that person are on; if no line through the bell, they are off