After poking around on google, it looks like Netspend is pre-paid debit card. Currently, Square is only able to support fully transactional bank accounts.
Pre-paid cards and accounts are not transactional, so we are currently unable to support them in place of a bank account. We require a transactional bank account in the event you issue a refund to your customer or a chargeback is presented to Square. You must link up a checking or savings account.
