I’m sorry if this information is somewhere else but I was able to access Challenge 8 yesterday and now I can’t. I don’t mind subscribing but I thought I got a bit more of Level 1 to try before the free content ended.
It’s just changed to only having the one sentence trial for free. It used to be free through Challenge 15, but SSi is taking a step forward! You can find Aran’s anouncement at the beginning of this thread here : The (almost) end of 'free' SSiW