Suddenly no playback sound on Ubuntu 20.04

I’m using Audacity 3.1.3 on Ubuntu 20.04.4. Until the problem, Audacity worked without issues. On the last two cold boots of the computer, Audacity had lost the playback device (Default) and was attempting to playback through an inoperative HDA circuit. When I tried to re-set preferences, “Default” was not an option in the drop-down menu. Each time, rebooting the computer and restarting Audacity brought “Default” back as an option and the program functioned normally. I suspect this may be Ubuntu’s problem, but I’m wondering if anyone has any ideas. Thanks. Iraj

It sounds like something is grabbing exclusive control of the default audio device. This used to be a common problem with some Flash web browser pages - perhaps there’s now some other browser plug-in causing a similar problem. Does the problem occur if you don’t open your web browser?

Thanks, Steve. Before I read your reply, I opened Audacity today and it was again using HDA as the device. I’m pretty sure I had the browser open at the time. I exited and reopened, but had to reboot the CPU before it gave me “default” as an option. After I read your post, I exited Audacity, exited the browser, and restarted without a CPU reboot. “Default” was still active. I’ll now try a CPU reboot.

OK: A cold reboot of the CPU did not affect Audacity this time, either with the browser open or with it closed. “Default” remained the playback device. However, on the reboot, an error message flashed – that I could not fully read – that said “input/output” error. And, for the second or third time, my Audacious playlists were unavailable; more to the point, the wired external hard drive where the music files are located “could not be opened.” So, I’m pretty sure the problem is on my end, not Audacity’s. Thanks again for your response.