By chance, I found an announcement here, yesterday
https://www.chess.com/forum/view/community/new-lessons-get-a-fresh-look
Hope this helps.
New lesson format
Sort:
Thanks Terry, that helps.
OK, so I found out how to access the old lessons, and it was right in front of me. On the lessons page, just below the top dialog box that says 'Start Lesson' is an easy to miss horizontal line with two options: "All Lessons" (which I think it defaults to) and "Guide". Select "Guide" and the old lessons will appear. The visual format is different but they appear to all be there, including the progress I had made. QED 
Thanks to the chess.com help team for getting back to me on that.
I've been on the site for maybe 3 weeks and have been dutifully going through my lessons but today when I logged on the lesson format has changed. It starts with a game from Kasparov and then a list of topics, each with a different chess expert talking. Maybe this is better but I was enjoying the old format, at least for now.
Is this the new format or did I enable some other lesson mode. I'm a bit confused as I didn't see any announcement.
Thanks in advance...