Inventory dont work on IOS

Hi, im working on my first ios game in UE4. Im done with the inventory system (array) and in the UE everything works. But when i package project for ios and pick up some item, it disappear but not in to inventory.

The reason is it cant find a free position in inventory array. In the UE, when i hit play, every thing works and “find item” node returns number of array position - 0,1,2… But in ipad it returns -1. Do someone know why and how i can fix it please?