Blur Image Effect doesn't work on iOS (Unity 5)

I have added a blur image effect (Optimized Blur from standard assets) to my game. It works perfectly in play-in-editor and PC builds, but on iOS (iPad Air 2 to be specific) the blur does not show up. It appears as if there were no image effect at all.

Is this a known issue? All the threads concerning this topic seem to be from 2011 at the latest. The Unity docs say that it should work on all engine-supported hardware.


Same issue, still no support?..

I thought this is a general IOS problem, but it seems to be a specific iPad Air2 problem.
I just tested my app on an iPhone5 and there is the blur working fine.

I just tested this on an iPhone 6s Plus, and there’s no blur effect. I tested it on a $80 Android device, and the blur worked!

When compiling for the iPhone 6s+, I chose Arm64, iPhone and Metal.

When I recompiled just changing from Metal to GLES3.0, the blur effect worked correctly and there were no XCode errors.

When compiled for Metal, XCode informed me that there were no fragment shaders, Blur wasn’t supported, there were variable name errors throughout all the shaders. It was a mess.