Hi,
I'm sorry to hear, you are facing trouble with it. We've already fixed it and until it'll be published, to apply that patch, please overwrite your local copy of the 
_fp_unkempt_lawn_corona.mat (located at 
C:\Users\<yourUsername>\AppData\Local\Itoo Software\Forest Pack Pro\lib\Presets\Layered_Lawns\matlibs) file with the one I’m just sending you by email. 
Let me add, that as mentioned in 
this post, which should help in this kind of trouble (if the preset doesn't have the 
Forest Edge map applied, you can easily fix it by going to the 
Material rollout and launching the 
Optimize Materials tool where make sure 
Apply Forest Edge is checked and click 
Optimise).
I hope that helps.
Best regards,