The digi-app allows you to do a transaction without using the currency. Therefore, you have to add money to the app, to allow you to do the transaction. If you’re not able to add money, then you can refer to various sites that’ll tell you the necessary steps to achieve your intent. If you’re still unsatisfied, then you can contact Cash App Customer Service for descriptive solution.
sprint-customerservice.com/cash-app-customer-service/