Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Illinois

We are legally married for more than 10 years. Now I have Walmart store credit card for about half an year. I called Synchrony Bank who issued the card several times to add my wife - - as a joint account holder but they refused. We have same household and marriage certificate and a number of joint credit cards and joint bank account since 2004. It is absolutely unclear why my wife can not be joint account holder and may be only authorized user without supplying her SSN and report to credit story.