Why does the market close every time the market starts to move?


I have started out with a demo account. I am finding myself frustrated when the market starts to move and i try to close a position i get an error message stating the market is closed? why is this? I wont use this site if it is going to freeze money everytime a position goes into the green. i tried to open a chat with Zulu and it seems like the chat feature isnt working? so here i am voicing my concern. As i see it i wont be opening a real money account if this is the way the site behaves when the market starts to move.

Thanks in advance.