I can't use the code editor

I have already reported this issue, but i am trying to start out with coding, but nothing seem to help me right now.

When i open a lesson (i have tried to open several, all having the same issue) the code editor seems to be all shadowed out. i can’t write any of the things that that site instruct me to do.

I have tried internet explorer, chrome and firefox. nothing seems to work.
Does anyone else have this problem? And do you know how to fix it?