You should check your account balance before concluding that the money transaction failed. If your amount has not been deducted from your Cash App account, check if the account balance has been deducted from your bank account. If the card number that you entered on the Cash App transfer page turns red, this may be due to the fact that you provided incorrect payment details for the recipient and this may be reason for Cash App Won`t let me send mOney. https://www.mailsupportnumber.com/blog/cash-app-wont-let-me-send-money/