Please check if the plugs for microphones/loudspeakers /headphones are connected correctly, and, if necessary, the devices have been switched on.
The "Mute" function must be deactivated for the microphone and speakers in the PC and on the external device, if applicable.
Privacy settings must allow the use of the microphone for desktop apps (Windows > Settings > Privacy > Microphone > Desktop apps).
Check and adjust volume settings (also on patient side).