hello sandraholloway113............ * Open Messenger. * Open a conversation. * Tap the video button. * Tap the camera swap button to switch between cameras ''Hold down the "Command" and "Option" keys simultaneously and then click on the "System Preferences" icon in the dock. Continue holding down the two keys.'' however the problem not fix follow this steps: On your Mac, choose Apple menu > System Preferences, click Security & Privacy, then click Privacy. Select Camera. Select the checkbox next to an app to allow it to access your camera. tell me its help thank you!