Why does OAuth return "unauthorized for this grant type" error?

Are you receiving the following error when you call the /oauth/token API to authorize your application?

{
"error": "unauthorized_client"
"error_description": "Unauthorized for this grant type"
}

To fix this problem, check the following:

Is your "application type" ==> "Web/UI based" or "browser-based application?"

If the answer is yes you will need to follow the 3 legged OAuth flow to authorize your application.

The authorization code flow provides the following benefits:

• a consistent and trusted UI
• integrated password reset
• integrated single sign-on (SSO) via SAML support

For more information please check out the following:

• Using OAuth 2.0 Authorization Code Flow to Access RingCentral APIs
• RingCentral's Authentication Guide in our Developer Guide