The cash app requires synchronization of using debit or credit cards for allowing the user to make online transactions with the help of this application. Sometimes users cannot able synchronize their respective debit or credit card with the app for some reason. If you also facing this issue then call on the cash app customer service .  The support team of the app will provide you the best tips for solving this problem. https://www.mailsupportcontact.com/phone-number/cash-app