黑屏：检查摄像头权限与是否选对设备；可先关虚拟背景。
无声音：看是否静音、系统输出设备是否正确。
等候室：联系组织者；确认是否用了受邀账号。
Teams 常见问：黑屏、无声音、进不去等候室
Teams FAQ: black screen, no audio, lobby stuck
Black screen: Check camera permission and selected device; try disabling background effects.
No audio: Unmute and verify system output device.
Lobby: Ask the organizer; confirm you used the invited account.