Back in 2014, Google launched a new app on Android known as "Device Assist" for Nexus, Google Play Edition and Android One. The purpose of this app was pretty self-explanatory. It would scan your device and make sure that nothing was wrong, and if anything was amiss, it would let you know as well as giving you steps to solve or rectify the issue. It was mostly basic things, like recommending a reboot. Which believe it or not, can actually help improve your experience on any Android device.
It appears that not enough users were actually using the app, and now Google is shutting it down. The app listing is still in the Google Play Store, but only for those that have installed the app previously. Additionally, the app is all but useless now. As the only tip it shows is the fact that it is being shut down. If you tap on that card, it will redirect you to Google's online tips site. Which is what was powering the app in the first place.
With Android 7.0 Nougat, tips like these are already recommended in the settings - at least with stock Android, this may be a different story once we start seeing manufacturers like LG and Samsung roll out the update - so it's not a big loss, for anyone that did actually use the app. Android 7.0 Nougat may still be a ways off for a good number of users, especially if they don't have a Nexus device, but luckily the tips website is still available if you do need some help.
When the Device Assist app was released in 2014, it was only available for Nexus, Google Play Edition and Android One smartphones. Meaning that only smartphones that Google pushes out the updates for, and these are also all stock Android smartphones. That appears to be the compatibility when the app got shut down as well. Which means this likely affects an even smaller amount of people than originally thought. The Device Assist app, like many of Google's projects, started out as a great idea but in the end, it won't be around for much longer.