ShaderLab GrabPass{} doesn't seem to work on iOS 8.0 and beyond.

So, it seems to me that the GrabPass{} function doesn't work on iOS 8.0 and iOS 9.0 . My shader worked on 7.0 but doesn't work on 8

Here is the shader, it's a simple mask that turn every color behind it grays:

-------------------

Shader "Custom/GreyScale"
{
Properties {
_MaskTex ("Masked (RBG)", 2D) = "white" {} //the masked texture.
}

SubShader {
Tags {
"Queue"="Transparent+10"
"IgnoreProjector"="true"...

ShaderLab GrabPass{} doesn't seem to work on iOS 8.0 and beyond.