Apple released a brand new iOS 11 update for the iPad and iPhone this morning that makes some big fixes to HomeKit.
iOS 11.2.1 comes a little over a week after Apple dropped iOS 11.2 on the public bringing Apple Pay Cash and a host of bug fixes. The new update is being released along with tvOS 11.2.1 to restore some HomeKit functionality after Apple patched a bug server-side earlier this week.