Hi there! At this time, there aren’t any reported issues with adding a payment method in the portal. However, specific devices/browsers sometimes give customers trouble. I would recommend having your client clear cookies/cache, or try a different browser or device, and see if they have success.
Note that a payment method can’t be saved until all required fields are filled out, which means the “Save” button is grayed out until that information is provided! If they continue to struggle, you could also add this payment method to their contact record - payment methods flow back and forth between the portal and Aspire!
