I have tried the call and video features on Upwork several times -- with no success. It's usually a sound issue (e.g. I can hear my client, but they can't hear me). Is there a way to do a test call (as Skype does) to make sure everything is working?
Could you please clarify if you are using voice/video feature on Upwork Desktop App or in a browser? If it's in a browser, which browser type/version you are using?