question

What is the from number you're using please and is it part of your production RingCentral account for the user you've authenticated in the session?

Could you provide the request headers and body you're using please?

Hey Ben, 

I am using the following as my request headers/body :

conn.headers['Authorization'] = "Bearer #{token["access_token"]}"   
conn.headers['Content-Type'] = "application/json"

and the body

res = conn.post '/restapi/v1.0/account/~/extension/~/sms', {      to: recipients,
      from: {phoneNumber: 'mainRingcentralNumber'},
      text: message
    }.to_json


in the above, recipients is a local phone number and message is just a string message
the from number is 5128272252 and we are using extension 101; we got those from the user accound credentials page on the ringcentral dev dashboard

The "to" property must contain a Caller-Info object that has a phoneNumber property similar to your "from" property.

Check the, developer guide here for more information:  https://developers.ringcentral.com/api-docs/latest/index.html#!#RefCreateSMSMessage

Sorry, it wasn't clear from the example. recipients is a Caller info object  and looks like this [{phoneNumber: '512XXXXXXX'}]

so 

recipients = [{phoneNumber: '512XXXXXXX'}]
res = conn.post '/restapi/v1.0/account/~/extension/~/sms', {      to: recipients,
      from: {phoneNumber: 'mainRingcentralNumber'},
      text: message
    }.to_json

Yes, that should work as expected. If not, please provide the headers and error message please.

also, incase it helps, this does work in the sandbox

the headers:

conn.headers['Authorization'] = "Bearer #{token["access_token"]}"    
conn.headers['Content-Type'] = "application/json"

The Body: 

conn.post '/restapi/v1.0/account/~/extension/~/sms', {      to: [{phoneNumber: 512XXXXXXX}],
      from: {phoneNumber: 'mainRingcentralNumber'},
      text: message
    }.to_json

the response/error:

<Faraday::Response:0x007fac88eb5a00 @env={:method=>:post, :body=>"{\r\n  \"errorCode\" : \"FeatureNotAvailable\",\r\n  \"message\" : \"Phone number doesn't belong to extension\",\r\n  \"errors\" : [ {\r\n    \"errorCode\" : \"MSG-304\",\r\n    \"message\" : \"Phone number doesn't belong to extension\"\r\n  } ]\r\n}", :url=>#<URI::HTTPS:0x007fac846bc438 URL: https://platform.ringcentral.com/restapi/v1.0/account/~/extension/~/sms>;, :request_headers=>{"User-Agent"=>"Faraday v0.8.9", "Authorization"=>"Bearer U0pDMDFQMDdQQVMwNXxBQUF5cjVEZURodDZhSWx2cGFYUlhsREJCdkd6Yzk5d0JEd3ZraExzNm5yNGl0YUt5bG5fRE5QX0Rtd0JobXl4MG16Qm9DRy04NzZPaDNPV3FzbEwwTUtuNHVYM3ZWR2xWd052cjZSYUdsbW93bmpXd3pyRkt3aFJrZTBGaEVGeDJVZ3xZNHl2WGd8YkdUYVhKZEpucGlYQnF0QndBRUs5UQ", "Content-Type"=>"application/json"}, :parallel_manager=>nil, :request=>{:proxy=>nil}, :ssl=>{}, :status=>403, :response_headers=>{"server"=>"nginx/1.8.0", "date"=>"Mon, 21 Mar 2016 19:32:46 GMT", "content-type"=>"application/json;charset=UTF-8", "content-length"=>"218", "connection"=>"close", "rcrequestid"=>"b06f05f4-ef9b-11e5-af18-005056973311", "routingkey"=>"SJC01P07PAS05", "x-loadmetric"=>"7", "x-error-id"=>"2da5f246-03f3-481a-8dd3-14a4df00e683", "x-rate-limit-group"=>"medium", "x-rate-limit-limit"=>"40", "x-rate-limit-remaining"=>"39", "x-rate-limit-window"=>"60", "content-language"=>"en-US"}, :response=>#<Faraday::Response:0x007fac88eb5a00 ...>}, @on_complete_callbacks=[]> => {"errorCode"=>"FeatureNotAvailable", "message"=>"Phone number doesn't belong to extension", "errors"=>[{"errorCode"=>"MSG-304", "message"=>"Phone number doesn't belong to extension"}]}

Awesome, thanks for sharing your success.

?? that was my error

it works in the sandbox but not production ...that was there production error

It is still not working

I received an email that this case was closed, is there a way to reopen it please?