3816305 - Error in logs: "Invalid frequent flyer number; 7-1709; eJPlus card number must be either 8-digits or the character 'S' or 's' followed by 6-digits " when booking Easyjet via Travelfusion

When I confirm my easyJet booking by clicking Reserve Flight and Continue I receive the error:
We're Sorry...
We encountered an issue that prevented us from completing your request.
We have encountered an internal error and are unable to complete your request. Please contact your company administrator to report this error, and contact your travel agency if you need immediate assistance with this reservation.

When confirming an EasyJet booking (via Travelfusion) by clicking Reserve Flight and Continue the errror "We're Sorry... We encountered an issue that prevented us from completing your request." is thrown. , KBA , CON-SRV-TRV-ADM-TVE , Travel Vendor Exclusions , CON-SRV-TRV-ADM-LAN , View Airlines , Problem