There are several operating systems being used, from 4.0 KitKat all the way up to 9.0 Pie. I have noticed some apps not working on certain operating systems. Each operating system will have bugs when it comes to certain applications. If a app does not work on your device, there's a chance it's because of the operating system you're running it on. Android 6.0, 7.1 and 8.1 seem to have the best overall compatibility with the majority of apps. Keep in mind that operating systems have more or less a 5 year span before some developers start to abandon older operating systems to concentrate on the newer ones.