curl -X POST "https://platform.ringcentral.com/restapi/oauth/token"Source:
-H "Accept: application/json"
-H "Content-Type: application/x-www-form-urlencoded" -H "Authorization: Basic <access-token>" -d "username=<user-phone-number>&password=<user-password>&extension=<user-extension>&grant_type=password
Here the problem you are facing is the header Authorization which is Basic <base64 of appKey:appSecret> .. If you pass that header in curl, your problem will be solved
Using the RingCentral Phone for Desktop, you can dial or receive test calls, send and receive test SMS or Fax messages in your sandbox environment.
Download RingCentral Phone for Desktop:
Tip: switch to the "sandbox mode" before logging in the app:
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