Need help troubleshooting app - not working on some devices

[vmnoodle71]

Lately I have been getting reviews and feedvacks of my app not loading up on some Windows Phones . I don't have any idea how will I solve this device specific problem . suggest some solution

Chat Stickerz | Windows Phone Apps+Games Store (India)

 

[Smartaps]

Do you test all the simulator device in Visual Studio ?