Updated video and video relay app (you’d know the actual app names): They both need to be installed before any further play sessions. Remember to fully uninstall the other versions so you don’t accidentally re-install the old apps. Download and install the new versions from the same locations. I’ve already replaced the old version. If you need the link again, ask via encrypted email. The update is important because if there are any conflicting devices around, the phones wont connect.
Updated instructions: Download again from same location. Chapter 21 has the updates, which explain how to use the updated apps. It’s only a minor change. Basically you find and enter the device name for the phone, so each phone knows which connection to accept.