After releasing iOS and iPadOS 13.4.1 yesterday to address a bug with FaceTime, Apple has today released watchOS 6.2.1 that comes with a similar fix.
According to Apple, watchOS 6.2.1 “fixes an issue where devices running watchOS 6.2 could not participate in FaceTime audio calls with devices running iOS 9.3.6 and earlier or OS X El Capitan 10.11.6 and earlier.”
The update for Apple Watch comes in at 41.6MB and can be installed by opening the Watch app on your iPhone, then going to General > Software Update > Download and Install.
In order to install a watchOS update, your Apple Watch needs to be on its charger and also in range of your iPhone connected to Wi-Fi. The update will install when your Apple Watch has at least 50% battery.