App works on S7 not on older Gear VR devices?

Hi,

I've been testing my Gear VR game on S7, I launched it on oculuskeys.com but most users are getting device not supported message. S6 and Note phones seem to not work with the app...

Has anyone seen this before?

I'm hoping it's something in the Manifest file or my Unity version...

Unity v5.3.4f1
 Oculus Utilities v1.3.2
OVRPlugin v1.3.2
Minimum Android API 19
Target Android API 23