环信初始化的时候，报duplicate_unique_property_exists错误

环信Android 的SDK，启动的时候调用了这个接口
http://182.92.228.160/wdjky/sheyecare/devices
然后返回了400
{
    "error": "duplicate_unique_property_exists",
    "timestamp": 1461824125437,
    "duration": 0,
    "exception": "org.apache.usergrid.persistence.exceptions.DuplicateUniquePropertyExistsException",
    "error_description": "Application 223f3410-dec1-11e5-b90d-9963ad226dd3 Entity device requires that property named token be unique, value of 392aa4e3-b1b1-3173-9eb0-5351173a0142 exists"
}
请问这是什么原因呢？