I was just replying to another thread where people reported the same issue, but then found this thread which seems to be more appropriate. I hope the following contains some useful pointers for troubleshooting. For reference, I'm running Enpass version 6.6.0 (770) on Windows 10 1909 (OS Build 18363.1379).
I have the same issue as reported here. After the recent update, I need to restart Enpass after booting my machine in order for Windows Hello to work. Just like Volkx showed, Enpass would show the 'Unlock with Windows Hello' screen, but the Windows Hello system dialog (see below) doesn't show. I've noticed before that Enpass usually opens a small window with a loading indicator right before the system dialog pops up, but that window doesn't show either.
I think there is a problem with Enpass trying to start the Windows Hello process right on starting (by which I mean the automatic open on system startup, not me opening the app manually): while the Windows Hello dialog doesn't show up, the infrared lights of my Windows Hello enabled camera do start lighting up as if trying to identify me. Only when restarting Enpass and successfully logging in using Windows Hello do these lights turn off again.
My guess is that Enpass starts the Windows Hello process, but somehow prevents the system dialog from opening. Until Enpass is restarted the Hello authentication process is blocked by this previous attempt, so Enpass fails when trying to initiate the Hello process again. Because the dialog is not shown, there is no way to cancel Windows Hello except for restarting Enpass.
What I mean with the Windows Hello system dialog: