“Closed Category” - unable to use sponsored listings for clothing

Can’t do sponsored listings on amazon europe for clothing.
It says the category is closed and sellers can’t “compete for buy box”

I can see that many sellers use sponsored listings in the clothing categories
Any ideas whats up?

To use sponsored products each child item will need an image even if they only vary by size for example.

Once you have added images to each of the child listings you should be able to use sponsored products.