We use multiple information points about the customer and the purchase to determine a customer's eligibility to use our service. We're not able to disclose the specific reasons why a particular order wasn't approved as it's a completely automated process.
The more customers use Zip and your site, the more data our risk assessment collects. That being said, we're constantly refining this process and are confident we've developed a tool that protects our merchant and customers alike.
For questions or assistance please contact Partner Support.