Android 5.1.1, released in 2015, is an older version of the Android operating system. While it's still functional, it may not be compatible with the latest versions of the Google Play Store. If you're experiencing issues with the Play Store on your Android 5.1.1 device, such as crashes, errors, or incompatibility problems, downloading the APK file manually can help resolve these issues.
Go to Settings > Accounts > Google → Remove your account → Reboot → Add the account again. Google Play Store Apk Download For Android 5.1 1 BEST
This is not a Play Store issue. The app developer has dropped Lollipop support. Your only option is to find an older APK of that specific app (e.g., YouTube Vanced or an older Spotify APK). Android 5