We recently changed the functionality of purchasing t-shirts, shirts, pants, and any other user-generated items. Previously, selling the item would result in the Robux immediately being available for your use. Now, they follow the same model as game passes and developer products.
There is now a three-day period where the Robux are pending and appear in Pending Sales under the Transaction tabs for accounts and groups. These items are now consistent with game passes and developer products.
Developer Relations Team