Steam Store - Purchases remaining in your Inventory

When purchasing content through the Steam Store, your purchase is initially added to your Steam Inventory. This content will not be applied in to your game until the content is 'consumed' when booting Sea of Thieves. 

But on occasions this can take a few attempts to be 'consumed'. If this occurs please attempt booting the game and progressing past the 'Push Start' screen a couple of times to see whether that solves your issue.

It may also be worth attempting to reverify the integrity of your game files to see whether that will allow the items to be consumed. To do this, right click Sea of Thieves from your games list in Steam and select Properties. Then from the properties menu select Local Files> Verify Integrity of local files. Once complete, just boot Sea of Thieves again

If the items remain in your inventory please contact https://help.steampowered.com/ for further assistance with your issue.