The latest Google Play Services update removes Trusted Places as an option in Smart Lock.
https://9to5google.com/2018/05/23/android-smart-lock-trusted-places-removed/
Trusted Places seems to have been removed as a Smart Lock option
https://www.droid-life.com/2018/05/23/google-removes-trusted-places-smart-lock/
It's back:
[We did it!] Trusted Places has returned to Smart Lock
