Welcome to the RingCentral Community

I am trying to authenticate, but i am getting OAU-222:

I follow this documentation: https://developers.ringcentral.com/guide/authentication/jwt-flow

App Name: RPA

Sandbox: +19293784076

HTTP Input:

{
    
  "url": "https://platform.devtest.ringcentral.com/restapi/oauth/token",
  "body": "",
  "method": "POST",
  "headers": {
    
    "Content-Type": "application/x-www-form-urlencoded",
    "Authorization": "Basic XXXX
  },
  "queryParams": {
    
    "assertion": "JWT KEY",
    "grant_type": "urn:ietf:params:oauth:grant-type:jwt-bearer"
  }
}

Then I get this error:

{
    
  "response": {
    
    "status": 400,
    "body": {
    
      "error": "invalid_grant",
      "errors": [
        {
    
          "errorCode": "OAU-222",
          "message": "Account does not exist"
        }
      ],
      "error_description": "Account does not exist"
    }
  },
  "request": {
    
    "body": ""
  }
}