Hey man,
I have fixed the problem you have been having it was due to mobile not supporting a number of the features in the HQ and MQ materials i have now add feature settings so that these features will not cause errors when trying to use the materials on mobile. unfortunately mobile does not support the advanced wind or interaction features of the pack (Due to software limitations) so the grass will switch to the new mobile wind settings, i will be sending the update to unreal tomorrow so hopely it will up soon, sorry for any problems this might of caused you 
Edit: The update will also have some cool new features to look forward too 