new Latitude E7450 : fingerprint reader first working occasionnely, now not working at all, despite using system restore to initial factory state

Hello,

I am the owner of a brand new E7450 for 2 days. It came with Windows 8.1 on drive.

It happens the fingerprint reader was not working at all from the beginning (before I had installed anything) : when I tried to Add Fingerprints under PC Settings > Accounts in Windows 8.1 it was not possible to register a fingerprint when asked.

From the beginning, I made a manual system backup using the Windows' "system protection" function.

Then I tried successive drivers removing/reinstalling/rebooting and ControlVault firmware upgrades (despite it was already set to version 30.7.27.0). I regulary restored the system to initial state when I was not certain of what I did.

It happens that after a firmware rewriting, I was finally able to register and test fingerprints succesfully. I thought the problem was solved, but after a few hours of use of the computer, the fingerprint scanning began to have faillures again and finally stopped to function completely, whereas I did not install any other software on the system during the period !

So I restored again the system to its initial factory state using the "system protection" function and restarted testing and removing/installing the drivers and firmware again. But I have'nt had a new success to this day : the scanner is back to no working at all, despite being correctly detected by Windows.

I also eventually tried to install the Dell Data Protection package using the Dell Digital Delivery tool, with no more success (I have restored the factory state since).

I am out of ideas now. I would like to ask a remote control assist for this issue.