I’ve just noticed that all reverbs that worked properly in 4.22 stopped working after updating to 4.23. Update to 4.24 didn’t help. I found this issue report: Unreal Engine Issues and Bug Tracker (UE-82641) , marked as Cannot Reproduce.
I answer myself: since 4.23 (or 4.22.3, I’m not sure) reverb works only when sound has any Attenuation added. Also, it is no longer possible to preview reverb in the editor by moving the editor camera inside the Audio Volume and playing sound from Content Browser.