Ok I had this happen as well, I tried calling customer support only to be on hold forever, so I hung up thinking OK I’ll try again tomorrow and then something happened in my neighbourhood and the power went out on my whole block when the power came back on I noticed that my sound was back on my doorbell camera so I think the answer is to turn off your main breaker in your house and then turn it back on and see if that helps. I’m pretty sure that is what fixed mine.