There are multiple reasons for which people complain that the Cash app won't let me send money. If you are experiencing the same then you have an insufficient balance in your account. Also, it is most possible that you have entered incorrect details of the recipient that is why you are getting this error. Customers can simply fix this error by entering the correct details and adding money to their cash app wallet. 

https://www.7qasearch.net/blog/cash-app-wont-let-me-send-money/