I just got this problem today right after I added two fingerprints. I tried your suggestion above. The only two apps I see under Device admin apps is Find My Device and Google Pay. Neither of those seem to be causing the problem. Help!
If the settings didn't work that longhiker provided above, I would recommend trying to put your device in safe mode, to see if you can access the camera without the error. By putting it in safe mode, this will let us know if it's a third party app that is causing the symptoms you're experiencing.
Did this and still same message in Safe Mode. This all started when I added the two fingerprints yesterday. What next?
I understand how frustrating this can be. Look to see if the sensor toggle is off. It's in the pull-down menu. Looks like an EKG with a line through it. It will say sensor off or on.
You can also try going to Settings -> "Biometrics and security" -> "Other security settings" -> "Device admin apps" you can see which apps may be blocking the use of the camera.
If you still are unable to use the camera I would recommend trying to put your device in safe mode, to see if you can access the camera without the error. By putting it in safe mode, will let us know if it's a third-party app that is causing the symptoms you're experiencing.
If the message still occurs in Safe Mode, service would be recommended. Please send a private message with the full model code and the IMEI number of the phone. http://bit.ly/2XERsky
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