If a user is seeing an error at checkout such as a 422 error on the screen, this means that there was an issue authorizing the card for the transaction.
This can be due to a number of reasons such as entering the card information incorrectly or the account not having sufficient funds.
The user should be able to add their card to their account and try again to confirm that the information was entered correctly. Or they can try using a different card and see if that goes through.
If they continue to have issues with this, please email firstname.lastname@example.org and we can take a look into the account to see what may be happening.