Huh. I just tried adding the USAA debit card for the joint account with my 15yo, and I again I was having to call to verify it. It was failing on entering my SS number, more like it wasn't hearing the tones (hmmm, I'm on wifi calling today - maybe that would be it?).
But even though the physical debit card looks different since it is a youth account, the Apple Pay image is the same. Drat.
I think I will jump off wifi calling and see if that changes the entering of the number thing.
ETA: yes, jumping off wifi calling fixed that issue, I did still have to call and activate and get the text. I wonder what the difference in some not having to do it is?
oh, and I did get an email this morning thanking me for adding the cards yesterday.