Apple has released watchOS 4.3 for the Apple Watch. You install it via the Apple Watch app on your iPhone. According to Apple the upgrade:

° Let’s you Control volume and playback on HomePod from your Apple Watch;

° Restores the ability to control music on an iPhone;

° Allows you to use any orientation for Nightstand charging mode;

° The Siri watch face now shows progress towards closing Activity rings and when new songs are added to Apple Music mixes;

° Resolves an issue where Activity achievements were incorrectly awarded for some users;

° Fixes an issue where Siri music commands were not working for some audio devices.