GoCardless Direct Debit

I have been setting up a membership form using Civi and Civi Webform - and the GoCardless civi extension from artful robot. However, I am getting an error at the callback stage - "Could not find a valid session key".

I was just wondering if anybody out there in internet land had had any success with this combination? It appears to be an old problem that has yet to be fixed, here is the issue on the extension page: https://lab.civicrm.org/extensions/gocardless/-/issues/32

If this is indeed a problem, it would be great to flag this up somewhere prominent.