I agree with this. I have the same issue I try to redeem my reward points and I can't redeem for an Amazon gift card. I accidentally removed my phone number and now I cannot add my phone number at all so I can't redeem for the Amazon Gift Card. What a rip off! You do all the things you need to do to earn reward points so you can redeem for a gift card and no matter how you try to resolve the lack of a phone number you cannot add a phone number. You keep getting either invalid phone number or use another verification and yet you have to use your phone number but you can't enter your phone number.
So frustrating. I guess I should just give up and realize I will never be able to redeem the points I earned for a gift card or any other reward other than a Microsoft based reward.