If you are unable to activate Cash App Card, then there can be multiple reasons behind the same. You might not be following the correct procedure to activate the Cash Card. Hence, read the instructions before activating the card. There are strong chances that the QR code or CVV number might be tempered or damaged. Sometimes, due to security reasons, Cash App temporarily hold the Cash Card activation process. 

The other possibility is also there that you may have not verified the Cashapp account as per the norms. If there is any violation of hiding facts, CashApp has the right to stop the services. The server down issue also plays a role behind the Cash Card activation decline. It is recommended to seek help from the Customer service and sort out things.