I can't open the library section

I registered a few days ago and while I am on a free trial plan. Yesterday I could see all of the materials in the library. Today in the library section I can view only those materials which I have chosen before.But the new material has disappeared. What’s the problem?

It sounds like you might be on the My Lessons tab. You should make sure you click on the Library tab either in the Learn submenu or in the left hand sidebar on any of those pages. If you need more help, just let us know.