Not something anyone else has reported, and general sound playback is handled by the simulator, so there’s probably nothing we can do if it decides to not work for you, unfortunately. You may want to get in touch with Laminar Research’s technical support.
The only other things I can think of is if you’re using a USB or wireless audio device that it’s disconnected or being disrupted somehow and the simulator isn’t picking it back up again. Or something else in your operating system is malfunctioning.