Create a case here by filling this form selecting the application in your Sandbox : https://developers.ringcentral.com/support/create-case
The developer support team will get back to you
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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