If the camera screen is pitch black and you don't see anything, it's possible that your app hasn't been granted access to the camera.
Please allow access to the camera from the settings.
Please note that the method of changing the permission settings may differ depending on the OS and its version, and in the case of Android devices, the display name etc. may differ depending on the device.
"Settings" app → "Apps for which you want to change permissions" → Turn on "Camera"
Check "Settings" app-> "Apps and notifications"-> "Apps for which you want to change permissions"-> "Permissions"-> "Camera"-> "Allow only while using apps"
If nothing appears on the camera screen even after granting the permission, please restart the terminal once.