on my carbon x1 I had to use fwupdmgr to update the Prometheus fingerprint device firmware. Additionally the firmware that was "current" in the repo didn't work and I had to allow using the beta or experimental version. can't remember exactly the steps I took to enable the beta firmware, this was almost 2 years ago as well, so it could be that that version is the now the correct latest version in the repo. after that I just installed fprintd and followed those instructions. But for sure it didn't work for me until I updated the firmware. good luck.