Hi Lars,
If Windows Hello has disappeared, it often means the device is no longer signed in with your Microsoft account or the sign-in settings were reset after an update or account change. You can usually get it back by checking Settings → Accounts to confirm whether you’re using a local account instead of a Microsoft account, and then signing in again if needed. After that, go to Settings → Accounts → Sign-in options to set up a new PIN or other Windows Hello method. There’s no separate download—Windows Hello is built into Windows—so restoring the correct account and sign-in settings is typically all that’s required.