There could be a number of causes for your user volume not to be seen on Discord. Your user volume settings may be off or set to a low volume, which is the most frequent cause. Make sure the slider is adjusted to the proper volume level by going to User Settings > Voice & Video > Input Volume to verify this. A problem with your audio drivers or settings could also be the cause of your user volume not appearing. Make sure your audio settings are set up properly and that your audio drivers are current. If the problem continues, it would be worthwhile to get in touch with Discord support.