If you entered some incorrect card number or CVV at the time of making any transaction, then you can see that the Cash app won't let me send money. Thus, at whatever point you will make any transaction, then you need to guarantee that you are enteirng the correct details and check it twice at least going before hitting the Pay button. https://www.email-contactsupport.com/blog/cash-app-wont-let-me-send-money