The "Cash App Invalid Card Number" pop-up is trying to inform you that your card has been blocked or discontinued by your issuer and is effectively an invalid card. If the cardholder says that the card is not locked, why does the cash say that your card number is invalid?
Also, why does the user face the Cash App invalid card number popping up error?
In general, Cash App invalid card number error occurs as a result of Cash App users inputting wrong card credentials while linking their card to Cash App account.