most time I cannot receive SMS

RC api returned successful response, but most time I cannot receive SMS, please see the below api response

return status: 201

{

"uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/account/665152005/extension/665152005/message-...;,

"id":1429594005,

"to":[

{

"phoneNumber":"+16304235427",

"location":"Aurora,IL"

}

],

"from":{

"phoneNumber":"+13234308604",

"location":"Montebello,CA"

},

"type":"SMS",

"creationTime":"2016-04-23T11:44:26.000 Z",

"readStatus":"Read",

"priority":"Normal",

"attachments":[

{

"id":1429594005,

"uri":"https://platform.devtest.ringcentral.com/restapi/v1.0/account/665152005/extension/665152005/message-...;,

"type":"Text",

"contentType":"text/plain"

}

],

"direction":"Outbound",

"availability":"Alive",

"subject": "verification code:2164",

"messageStatus":"Sent",

"smsSendingAttemptsCount":1,

"conversationId":6361148894337916524,

"conversation":{

"id":"6361148894337916524",

"uri":"https://platform.devtest.ringcentral.com/restapi/v1.0/conversation/6361148894337916524";

},

"lastModifiedTime":"2016-04-23T11:44:26.934Z"

}