Hello,

Since this morning I can not play any piece of music in my playlist loaded, be it in Amarok, Clementine, Juk, Qmmp: the interface with buttons seem frozen. Of course, I tried with keyboard shortcuts but it does not work better. I tried restarting the application, it does not work better. I restarted the PC. Not better. VLC I have no name more, but by then the interface reacts against. What can I do please?

//EDIT : no reaction too in Juk and "Musique"
//EDIT : no reaction in Youtube, in my browser, and no podcast. No sound and no scrolling from the progress bar.

This is a reply with a workaround that comes almost two years after the question, and I don't know how relevant it is. I am using KDE Neon 5.12 usually with Wayland login, and I have occasionally, with one of many PCs, had a problem that at least superficially is similar to the title of this thread--"interface does not play sounds and does not start". This concerns Firefox and not just Firefox but also its (to me, preferred) related open source browser, Palemoon. On this PC, sound is suddenly not coming at all from the browser, although it works with such as VLC. This problem persists even after reboot. The problem may re-arise as soon as there has been a 'sudo apt upgrade' of all software including the browser (possibly it arises in other circumstances as well).

The workaround, for this problem that concerns this PC with its browser, in this version of KDE is, however, surprisingly simple:
* open up the volume control and select 'Applications'
* regardless of how much the volume is set to, click on it and move it
* the instant the relevant controls are moved even a millimeter, browser sound is again functioning and will do so at next reboot

(The purpose of this comment is both to give this workaround further to anyone else who might need it, and to suggest to developers (possibly the Wayland developers) about a possible issue that it would be great to see that is "cured" in future versions.)