i’ve seen this post and the
HDR mobile didn’t help.
Basically my problem is that it works fine while I preview it in my desktop with the VR preview.
If I deploy it though, the materials turn black. The material I’m using right now is the refelction material, which I’m using to make a mirror.
Is it the device causing this trouble, or is the unreal doing it. 
my version is 4.12.5 android is 6.0