Even in the case as a server error occurs during the exchange animation, the cubes or items you acquired with the cube should have been properly sent to your Present Box. Please double check your Present Box from the Items menu.
Please note that in the case you acquired a duplicate item, it will change the item to a ticket you can use to exchange for an item of the same rarity of the duplicate item instead. You can check the number of tickets you have from the Cube Menu.
If your items aren’t properly displayed in the above locations, please provide us your support ID from the following location.