To activate Cash app card, first, you need to get a Cash Card. And, to get a Cash Card, you must 18+. If you are younger than it, then your application gets canceled for getting a Cash Card. If you are eligible to get this card, then go to activate it. You can activate it by using a QR code or without QR code. https://www.monktech.us/blog/how-to-activate-cash-app-card/