The error message being reported is based on the following in the documentation...
The link to the full documentation can be found here...
https://support.brixly.uk/en/knowledgebase/article/how-do-i-sell-domain-names-through-whmcs
To set a default payment method for your account, see the article below...
https://support.brixly.uk/en/knowledgebase/article/how-do-i-set-a-default-payment-method-for-my-future-invoices
Domain Reseller - No payment method selected - Fix
