How can we create custom greeting?

Hi,

We are using the (https://platform.devtest.ringcentral.com/restapi/v1.0/account/accountId/greeting) API .we need to set the custom greeting when any of the user make a call to our account. So in this case we are getting some error -

We are providing the details as shown in the screenshot.

Could you please suggest the solution how we can resolve it.