Here is the manual in English for your model.
Built-in RealSense cameras are unfortunately much harder to fix than the USB cameras when they stop working. I usually recommend in these cases that a recovery boot is done (a special kind of Windows restore provided by the manufacturer that restores the machine to as-new, with all the software and drivers that came with it, including the RealSense camera drivers).
Lenovo have a system installed on some of their products called OneKey. It accesses a hidden partition on the hard drive to restore the machine to factory defaults. This partition can be lost if the hard drive is wiped to reinstall Windows. But as you have only done a rollback, you may still have the recovery mechanism installed on your S5.
Reading the manual, I could not find evidence that your particular model has OneKey. But it does apparently have a similar system for completely restoring the hard drive to factory-new. Page 97 of the manual describes it under the heading 'Restore your hard disk drive to the factory default settings'.
I would strongly recommend backing up any personal / work files you have on your S5 before doing a factory restore.