Audio applet in tray is not visible. There is only empty space with no reaction to mouse clicks. The interesting thing is that every new system tray applet contains working audio applet only till next system reboot. Reproducible: Always Steps to Reproduce: 1. Add new system tray applet. 2. Experience working audio applet :) . 3. Reboot system. 4. Experience not working audio applet :( .
As you can see here https://www.reddit.com/r/kde/comments/3winhb/plasma_55_issues_broken_widget_frames_sound/cxwh41j I'm not the only one that encountered this.
I have the exact same bug.
*** This bug has been marked as a duplicate of bug 352055 ***