It seems we have a repeated issue with Purple Shulker boxes.
When the item is bought in the store, there is a risk that the item is not arriving in your inventory.
So far I could not replicate the issue, but the result is clearly logged when it happens. So in case you did not get your shulker box, please let me know and I will get you your money back.
For now I have updated the log file system to better log the exact command that is used to give you the item. I hope we’ll be able to fix it.