Precision M6800 - Fingerprint sensor does not work

Hi all,

My M6800 is in excellent condition and still under warranty.
Since i acquired it, i had never used its fingerprint sensor.
The machine was came with win7 pro 64b preinstalled, but some time later i installed
also win10 pro 64b in a separate partition, making it a dual-boot system with win7/10.
I had no any issues in both OSes, until recently where i decided to make use of the
fingerprint sensor.
After several attempts, i can't make the sensor to react when i put my finger on it,
to enroll it as a login option. This behavior is the same in both OSes.
In few words, just nothing happens when i put and lift my finger on the sensor or swiping it.

I have all the appropriate device drivers installed and everything seems to be ok:

Device manager in win7

win7, when i open the relevant application via Control Panel, to setup the sensor

win7, step before last

win7, last step. Following the instructions here, nothing happens..

win7, accessing the sensor via "Dell Data Protection | Security Tools"

win7, the same here, following the instructions nothing happens..

Device manager in win10

This is the enrollment interface in win10. However, by doing what it prompts me, nothing happens..

Thanks in advance for any help.