Send SMS FeatureNotAvailable after moving App to Production

We just moved our app from Sandbox to production. We have no issue with sending SMS to any number in Sandbox but it's not working when we switched to production.

Here's the error:

Exception: The requested feature is not available SDK HTTP Error at https://platform.ringcentral.com/restapi/v1.0/account/~/extension/~/sms Response text: { "errorCode" : "FeatureNotAvailable", "message" : "The requested feature is not available", "errors" : [ { "errorCode" : "MSG-242", "message" : "The requested feature is not available" } ] }

What am I doing wrong? Thanks.