Google Play Music is now beginning to have some issues in Android Auto. This is after the Galaxy S8 on Verizon was having issues in playing Spotify in Android Auto. The Google Play Music issue seems to be much more widespread, however, and not limited to just one device on one carrier. The Google product forums are filling up with users that are having the issue where "Google Play Music Doesn't Seem to be working right now", and there's no real way to fix this. We noticed this issue with Android Auto and with multiple devices, so it's definitely not just a handful of people, but it appears to be the vast majority of Android Auto and Google Play Music users.
All that Google is saying right now is that it is looking into the issue to find the root cause and get it fixed. In the meantime, it is attempting to collect as much information about the issue as it can. Which includes finding out the year, make and model of the car affected. Whether the user is using a head unit or not, as well as the version number that the Android phone is running and the Google Play Music app. This way Google is able to pinpoint which users are affected. If you are experiencing this issue, be sure to head to the Google product forums linked below and make sure your voice is heard. It helps Google gauge how many users are affected and get a fix out as soon as possible.
Google Play Music in Android Auto is a pretty popular task, although the number of people actually using Android Auto is still quite low. Partially because most people would just rather use their phone normally in the car. Not to mention the Android Auto interface is a bit clunky on such a small device. This is because Google wants large touch targets to make it easier to use when driving, so you aren't distracted. Android Auto isn't a popular product yet, but there is still a big group of people using the service, and they'll want this issue fixed soon.