Are you self hosting or using invoiceninja.com? There was a problem without GoCardless integration however it should be fixed in our latest self-host release. We hope to deploy to invoiceninja.com in about 10 days.
Unfortunately, Invoice Ninja currently only has an integration with the previous version of our API. You’d need our old style credentials – which wouldn’t currently be available to an organisation registered on our newer product.
Apologies for nay inconvenience – let me know if you have any further questions here.