Here you can see in the creator hub one of the masks not showing.
The group owner does not have premium, but these are all limited items for an upcoming game release. From the announcements on the premium requirement it should not be taking limiteds off-sale.
Hi creator, thanks for bringing this up to our attention, we have identified the source of the problem and fixed it. You should see your items showing up on the marketplace and group store now. If you are missing one or two items, it will eventually show up later, please be patient. Thank you for your patience.