You are trying to configure Audio/Video settings in Reacts but there is no microphone and/or speakers available from the drop down list when opening Audio/Video settings window:
Plus on Taskbar Windows sound icon shows red cross (no speaker or headphones are plugged in) though you have speakers/microphone/headset/camera properly plugged in .
This issue might be caused by a software drivers coming with some sound cards or audio/video devices (for example Beats, Realtek).
To resolve the issue please access Audio Manager Software that was installed with sound card or audio/video device and configure Audio/Video settings from there (for example setting your desired device as primary, removing any device that is not being used).
Close and re-open Reacts.