I have a homekit enabled August lock. A few weeks ago the Siri command to lock my door stopped working. I receive an error saying that the device does not support this function. I can still unlock the door using Siri but I cannot lock the door.
I have no experience with this lock, and since no one has answered you yet I went ahead and did a quick Google search. It's been recommended to remove the lock and completely reinstall from scratch. Let us know if that helped you any.