Cast to ChromeAudio fails while cast to Google Home works from Plex on Chrome browser

Plex Media Server Desktops & Laptops
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1

Server Version#: 1.16.5.1554
Player Version#: 3.104.2
Casting to Google ChromeAudio from Plex on Chrome browser fails. Worked up until this version (not sure when it stopped working).

Casting to Google ChromeAudio still works from non-Plex Chrome browser tabs.
Casting to Google Home works from non-Plex and Plex Chrome browser tabs.

Is there a weird incompatibility between ChromeAudio & Plex?
This is a new failure (9/2/19).

Thank you for any hints. I’ve reset everything.

2

Known issue. See Cast from Android app to Chromecast Audio broken.