I just observed this on nightly 2020-07-08 on Windows 10 on mit.webex.com (which is running version 40.6.1.179). (As noted before, the workaround of switching tabs made the audio start.)
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I just observed this on nightly 2020-07-08 on Windows 10 on mit.webex.com (which is running version 40.6.1.179 of the Cisco Webex Meetings Web App). (As noted before, the workaround of switching tabs made the audio start.)