Unity hub learn tab displays nothing

I'm a beginner in unity, trying to figure it out by unity learn. I read that I'm supposed to use micro-games to start learning this game engine, but when I open the learn tab in unity hub, there is nothing to display on this tab nor the project tab neither on the tutorial app. Can anybody help me with this asap?! (I should add that I have not signed in in unity hub, because each time I sign in, nothing happens.)