I login in RingCentral WebPhone Demo https://ringcentral.github.io/ringcentral-web-phone/
than i Received a call from partyA and after that I click on start conference button to start conference call and I also make call to another caller partyB then pop up get open and I again click on start conference button but my conference call not start tell me the correct steps line by line to test the conference call functionality on demo app