When you are receiving the error trying to add your card, please make sure to visit this link to make sure you are not running into any of these common reasons: https://community.secondlife.com/knowledgebase/english/billing-r11/#Section__7
If you are receiving an error when trying to update the payment method on file, you will want to make sure the payment method you are updating to is a supported method in Second Life. Here are the accepted currencies and payment methods you can use: https://community.secondlife.com/knowledgebase/english/billing-r11/#Section__3
Note: Please be advised that majority of prepaid cards are generally not supported in Second Life.
If the payment method you are wanting to use is supported by Second Life and you are still experiencing issues, here are some steps to try when adding the card:
- If you are attempting to add the payment method using a Third-Party Viewer, such as Firestorm, please attempt it in the Official Viewer.
- Attempt the transaction using an alternate browsing program (IE. Chrome, Internet Explorer, Safari).
- Clear the History, Cookies and Cache of your preferred browser, then attempt the process again.
- Associate your card with a PayPal or Skrill account.
I have tried those steps, and I am still receiving an error.