Since I played around with smart lock, my device just does not lock anymore. I disabled smart lock, I cleared all credentials, I removed device administrators, accessibility accesses (Lastpass). Nothing helped.
Can anyone give me a procedure to reset this setting?
Actually the thing I missed is that I was so annoyed by the double lock screen that I used the system profiles feature to create a profile which disabled the lock screen completely. Once I re-enabled the lock screen everything returned to normal.