Did you try reinstalling 8 Ball Pool? Usually, reinstalling an app fixes it. Make sure 8 Ball Pool is uninstalled so you can reinstall Game Guardian and hide it via VirtualXposed. If you're on an older device, you could use App Hider.
Edit: Then after hiding Game Guardian, install 8 Ball Pool outside of VirtualXposed. Go to Game Guardian in VirtualXposed, tap fix it, tap "Use root in Virtual space". Tap "Yes (dangerous)" and confirm you want to use root in the virtual space. Make sure your device is rooted to hide Game Guardian.