If the Cash app won't let me send money, the first thing to think is whether I have entered the right credentials, or incorrect details of receivers of money. It’s a suggestion for users who can recheck the details of recipients, and try to send money again. Also, you can try connecting your device to the Wi-Fi or router for uninterrupted services. Also, ensure to update and start the application again in case you face the issue even after connecting it to mobile internet.