When Threadless adds new products everyone who has an artist shop should go through their designs and enable them on new products and colors. It’s what I do regularly.
Threadless recently added Women’s Scoop-Neck Regular t-shirts which they wrote about. It also looks like there’s a new kind of hoodie: Classic Fleece. I don’t see them mention it anywhere so maybe it’s not yet available in all artist shops. I remember that when Threadless introduced face masks there were not available in my store at first so maybe they haven’t added Classic Fleece to every shop yet? I don’t know, but it’s probably a matter of days.
The easiest way to enable new products on all your designs is to go to your Shop Dashboard, and then in the Artist Shop section hover over Products and choose which products you want to edit. You will see a list of all your designs and just have to choose colors for each: