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Hello, I have setup my first app with 'private' and 'server only(no UI)' and tried to test sending a fax under sandbox env. The first request went out and put into queue, however when I try to retest the same request, it gave me an error. Please advise. Thanks.

==Error info

WWW-Authenticate: Bearer realm="RingCentral REST API", error="invalid_grant", error_description="Invalid resource owner credentials"

RCRequestId: bb6be21c-286b-11ea-9d35-005056bbcdd9

Pragma: no-cache

Cache-Control: no-store

AceRoutingKey: sjc11-c01-ace11.8e816ecd-0d3b-11ea-9962-005056bb6e9b

RoutingKey: SJC12P01

{

"error" : "invalid_grant",

"errors" : [ {

"errorCode" : "OAU-140",

"message" : "Invalid resource owner credentials"

} ],

"error_description" : "Invalid resource owner credentials"

}

== my setting

static String RINGCENTRAL_CLIENTID = "app cient id";

static String RINGCENTRAL_CLIENTSECRET = "app secret";

static String RINGCENTRAL_USERNAME = "sanbox number";

static String RINGCENTRAL_PASSWORD = "sandbox password";

static String RINGCENTRAL_EXTENSION = "101"; //from sandbox

public static final String SERVER = "https://platform.devtest.ringcentral.com";