If the system is in warranty, call Dell to arrange a repair.  If it's not, the service manual is linked below -- make sure the cable connections between the display and camera and the mainboard is intact.   If the cable is damaged, the display assembly will need to be replaced. Service manual here: [URL]  
I've tried everything I can find, including a system reset, but the camera sensors continue to have problems ( a Device_Power_Faliure / code 10 for the second sensor and a code 51 for the first sensor), leading to a "camera not found" error when trying to open up the camera app. I've uninstalled both and the camera and restarted, updated to the latest camera and sensor drivers and system updates, with no luck. Is there any other way I could resolve this?  
XPS 13 9315, camera sensors: OV01a and OV01A1B not working