Updating an Event Response in an Event's Audience.

Hi, 

We would like to manage our event by using Creatio, with the following flow, using a marketing e-mail and a process.

The flow is: 

1. A marketing e-mail is sent to the contact (Invitation).

2. When clicking on the e-mail's link, the contact goes on a landing page where he can submit his informations. Once this form is submitted, the contact is added to the audience of the event, and he receive a confirmation e-mail containing a QR code. 

3. The day of the event, the QR code will be scanned at the entrance. This QR code lead to a second landing page, where the hostess can validate the contacts informations. AT THIS POINT, THE CONTACT "EVENT RESPONSE" IN THE EVENT AUDIENCE SHOULD BE UPDATED FROM "PLANNED" TO "PARTICIPATED". 

--> And this point doesn't work, in all the tests we've made, all the contacts are stuck at the second landing page step...

4. Two days after the event (after the event's response would have been changed from "planned" to "participated", the contact would receive the last e-mail to thank him for his participation.

Info:

-The "modify Data" element is used to updated the event response after the second landing page is submitted. 

-The email containing the confirmation of the inscription to event (including the QR code) is generated by a process, and is not part of the marketing campaign. 

Any one of you could help us to resolve this issue? 

Any other solution that the one we're currently trying? 

Thank you very much for your help! 

Best,