New text notification issue for one specific contact on my iPhone 12 mini

I have an issue that I can't figure out how to fix. Recently (within the last year) I've stopped getting any notification except the red bubble when one specific contact texts me. My 12 mini iPhone still dings when any other contact texts me, and I get the red bubble notification that I have received a text but I don't get the ding and the text doesn't show at the top of my screen if I happen to be using the phone when the text comes through. I can be using another app, looking at the screen, waiting for a text response from that single contact and not realize it has come through. I have to get out of whatever app I'm in and keep bouncing back to the Home Screen to see if my red bubble for notifications has changed numbers. It's really frustrating because my friend is mostly deaf and it's easiest if we communicate by text because he can't hear well on a cell phone call, but unless I sit staring at my text message screen for his response then I keep missing it. I've checked everything I can think of to make sure all my notifications are turned on and it only happens with this one specific contact. I get dings and vibrate notifications for every other contact except this one and it's driving me batty. Help!