List Builder > Select Data Store > JSON API > Configure JSON API - Next Button Disabled

Hi,

When i configure List Builder with JSON API, the Next button in Configure JSON API is disabled. I could see the log that the system pulling json data thru given URL in debug mode. my configuration as below.

Base JSON Object Name for Multirow Data: data

Total Record Count JSON Object Name: total

Primary Key: fieldActivityId

REST service response:

{
    "total": "2",
    "size": "0",
    "data": [
        {
            "badgeNumber": "D2732193",
            "creationDateTime": "2016-07-18-14.52.11",
            "scheduledDate": "2012-04-08",
            "serialNumber": "2732193",
            "fieldActivityId": "8633506304",
            "lastReading": "0.23",
            "dispatchGroupDescription": "Meter Read Team"
        },
        {
            "badgeNumber": "D8080983",
            "creationDateTime": "2016-07-18-14.52.11",
            "scheduledDate": "2012-04-08",
            "serialNumber": "8080983",
            "fieldActivityId": "8486861486",
            "lastReading": "0.78",
            "dispatchGroupDescription": "Meter Read Team"
        }
    ]
}