Today Apple has made iOS 11.2.1 and tvOS 11.2.1 available to download and install. They should already be rolling out over-the-air to supported mobile devices and Apple TV consoles.
Both of these releases practically fix the same thing: the inability to use remote access in HomeKit for shared users. This was temporarily disabled last week through a server-side switch, in order to swiftly address a newly discovered vulnerability in Apple’s smart home framework, which allowed unauthorized access to occur in certain conditions.
It was a pretty nasty bug, letting unauthorized people access your home accessories including locks and garage door openers. After applying this update, you will be able to once again use remote access in HomeKit, with no security-related downsides.