What causes sound to disappear on a Macbook Pro?

Question

macOS

The situation is the following.
Left the laptop on for half an hour unattended.
Then I sat down to work, decided to listen to a voice message in whatsapp, I realized that there was no sound.
I checked in the browser - the music does not play either. Well, more precisely, it plays, but there is no sound.
No errors, native speakers are selected. Volume is on. Rebooted the sound, the sound appeared. Ran diagnostics, no errors.
Who faced something similar?
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Catalina 10.15.6 (19G73)
MacBook Pro (16-inch, 2019)
2.3 GHz 8-core Intel Core i9

Answer 1

It happens like this, Macbook Pro 13 2018 2.3 GHz 4-core Intel Core i5 processor, Catalina 10.15.4 is connected to an external monitor, win 10 is always in the virtual machine, reboot also helps, I sin either that the external one is connected or on Parallels, with I did not notice the work only in Macos and without external loss of sound.