Go inside and set the viewing permission settings to see if the camera has permission.
After making sure that the phone is not covered, you can restart it.
If restarting the phone doesn't work, you can refresh the phone or upgrade to the latest version. Note that this operation will empty all the data and need to be backed up first.
If none of the above works, go to Meizu store for inspection and maintenance, and you can repair it for free during the warranty period.