Hello, It will be my pleasure to assist you with your computer today.
If this is happening on YouTube videos, then most likely the audio within YouTube got muted. Click the audio button in the lower-left area of the YouTube video to bring the sound back. I've highlighted the button in a screenshot here.
Since it shows you're offline in the chat, I'll switch our conversation to a static page. You'll still be able to reply there. Please refresh this page by pressing F5 if you're still in the chat.