Check the recipient details: It is important to double-check recipient details, as errors in the cash application will not allow me to send money in payment of the cash application will be a major cause of failure. Make sure you enter the correct information. Use a valid card if Cash app won't let me send money: You must update your card information when the card expires, and a new card must be connected to the Cash application. However, you should visit our website for a cash application issues.