Change payment method for iCloud storage

I know this has been asked (and resolved) in many previous posts but none of them provide a solution to my situation. We had a joint Apple ID for many years with our phones both connected to it. That was until the Apple Card came out. In order for both of us to get an Apple Card, we had to have separate Apple IDs (this might have been prior to the "family" version of the Apple Card account). I created a new Apple ID for myself, unhooked my phone from the shared account, setup up iCloud storage (basic 2TB plan) and assigned a payment method. I am on a family sharing plan with our original account so I can share music, photos, etc. Now I wish to change the payment plan for my iCloud storage but the methods defined in most all of the other threads do not work for me. I get to the window to add a new payment method but the selection is grayed out. The other interesting thing is that my current payment method is not shown in the window either. I need a way to change the payment method 1. so I can define a new one, and 2. so I can update the expiration date should I use a credit card for payment.