What credentials should I use? OR I am getting an "Invalid resource owner credentials" error

"Invalid resource owner credentials" error usually occurs when the credentials are incorrect. Please try logging in to Service web (service.ringcentral.com) using the same credentials (username, Extension and password) you are using to authorize the application to make API calls. If your password is incorrect, you can reset it yourself by clicking the Forgot password link. You can go ahead and do that by clicking on the Forgot Password link.

Also if your application is in production, you need to switch all your credentials from sandbox to production.

To Verify this,

• Login to developer.ringcentral.com
• Go to Console, click on your app and on the Dashboard go to View All Credentials.
• Please confirm that all the credentials API server URL, CLient ID Client Secret Username and Password are all from Production as shown in screenshot below

Please note that the extension provided in the developer portal is a default extension 101 which never changes and may not be your extension.. So for extension, use the one that you are trying to login from your code. To get the correct extension number you can also login to service.ringcentral.com (for production) and service.devtest.ringcentral.com for (sandbox). The password that you input should be associated with the extension.

Use the correct extension:

Please note that the Extension you see in the developer portal console (above image) is the admin default extension OR the extension that was created first in the system.

Each user has their own extension and a password associated with that extension. In order to see which extension to use, you must check your profile

you can also look at the extension when you log into service.ringcentral.com with the correct extension and password.