This seems to be a security issue on the part of Apple. A geofence automation or Siri will not unlock a door or open a garage door without first unlocking the iPhone. Presumably the concern is if someone has your iPhone without your permission they could unlock you door without your knowledge by entering the geofence area or asking Siri (if it’s configured to allow that from the Lock Screen).
If that’s not a concern you can do what I did (got the idea from a Reddit thread). I set aside a power outlet plugged into a rarely used socket and made an automation for when “An accessory is controlled” to lock the door when the outlet is powered on and unlock the door when the outlet is powered off. I labeled the outlet “DoorLock”
For Siri to unlock the door I say “Turn DoorLock Off” and vice versa to lock. The geofence automation turns the outlet on and off as needed, activating the door lock.
In addition to those automations you need to keep the outlet in sync for when the door lock/garage door are operated manually. I created two more automations for when “accessory is controlled”. When the door is unlocked manually it sets DoorLock to off, regardless of its state.. Manually locking the door turns DoorLock on.