I think theres a bug in this lesson. Running the app on an iphone. Challenge 4 of 5 shows a completely reset chessboard with the directive “white to move”. I tried every opening move and it rejects them all. So I cant move past this challenge, and thus the lesson. Anyone know whats going on?
Using an iPhone as well, the first time I did that particular lesson all the challenges worked perfectly. I decided to revisit that lesson a few weeks later and ran into the same bug. I ended up logging out of the app on the phone and logging back in and it worked. Might work for you as well