Store Products and Store Orders issues of Commerce_marketplace module
If you go to user/%/store(or by clicking the stores tab in your user page), you will be able to see the stores of the particular user. On clicking the store name, you will be re-directed to a page commerce_store/store/%storeid.
In this page, there will be diffrerent tabs View, Edit, Delete, "Storename"'s products, Memebers and Sales tab.

On clicking the tab "Storename"'s products, you will be able to see the products added to your store.

Also please double check that you have enabled correct permissions.

One thing though, admin will not be able to see the products of another user via the above method. He will have to naviagate to structure->Entity type -> commerce store ->store and click on a particular store name to view that store's details.

Let me know how that goes.