No sound when locking windows

Good evening Dunlock,
Thank you for all that information; however, I still have a question: which version of FxSound are you using?
Version 1.1.19.0 is available on fxsound.com and the Microsoft Store, or, alternatively, you can use the “Check for updates” function in the Help section of the Settings menu; and version 1.1.20.0 has been released for testing a few days ago.
This is the main thread on the known issue with sleep mode:
Speaker Output Changes to FX on wakeup with no sound
So far, no permanent fix has been found, but four actions can be proposed:

  • Disable all unneeded devices (including hidden ones) in Windows Sound Settings;
  • Disable automatic switching;
  • Change the Power settings to make the computer stay awake longer;
  • This workaround suggested by user @metanoiance.