In order for attendees to be imported to your Eventsforce mobile app, they must first "opt in" to participate. This allows the attendee to have control over what happens to their data.
You must create the "Mobile app opt in" question in your Eventsforce account, and add to each event which is using an app. The question will be a single check box that attendees can enable to participate.
Adding the mobile app opt in question
Follow the steps below to add the opt in question to your event:
Go to Website > Content > Registration Pages
Click to "Edit" the page that should contain this question
Hover over "Add here" and select "Registration question"
Type "Mobile app opt in", select the question from this list if it already exists, or click "Add" to create as a new question
Set up the question using the below settings:
Database name: Mobile app opt in
Question: Available to all events
Answer: Apply to this event only
Question type: Checkbox
Notes
Only the attendees who have opted in will be imported into the Eventsforce mobile app when using the "Event data integrator" option.