I just had the same issue, so I installed an Ultimaker Printer profile and low, the materials installed from the market place appears.
I then had another thought that the Ultimaker uses a 2.85mm Compatible material diameter. So I changed my custom printer profile to have a 2.85mm material diameter and yay! The materials appear against my custom printer.
This then lead to a third thought, while the material is available to now edit against the custom printer why not change the material diameter of the market place installed filament and return the custom printer back to 1.75mm. And there lies the solution. It's just looking at the material diameter.
I'm wondering if this should be an enhancement request for a tool to allow showing of material types of diameters which don't match your current printers compatible material diameter?