Parsec has no speaker to capture on the host If that fixes it, but you want to prevent guests from hearing themselves, use the VB-Cable fix in the echo article. The host can try turning the feature off in Parsec's settings > Host > Echo Cancelling. Parsec's automatic echo cancelling may cause the audio to be lowered permanently if it detects someone's microphone is always active in Discord. Parsec's echo cancelling is lowering the audio Make sure that the overlay on the guest says 'Sound ON' instead of OFF. Open your computer's volume mixer on both the guests and the host, and make sure that Parsec and everything you're expecting to hear isn't muted or set to some inaudible volume percentage. Programs are muted or set to a really low volume
Right-click Parsec's icon in the taskbar and click Restart, on all devices involved. Sometimes all you need is to restart to get things going.
Restart Parsec on both the host and guests This article goes over potential reasons for why a guest cannot hear sound when joining a computer through Parsec.