This is typically caused because the donor's address information does not match the address the bank has on file exactly.  As a result, the transaction attempt fails the address verification settings, as established by the organization for the form. 

For example, if the bank has "Avenue" and the user entered "Ave", it would cause the payment to fail if the security setting on the form was 'Require both address and zip/postal code verification'. 

To resolve frequent failed transactions, a Sphere administrator may want to edit the Credit Card Verification setting in a form to 'Require address or zip/postal code verification'.  This typically resolves the user's donation experience and maintains a high level of security, especially when CAPTCHA is enabled