This happened to me as well. I have a thought as to why. When collecting (after a "start all" activation), I notice that the workshops "pop" up as complete a few at a time, as if they were started a few at a time, rather than all exactly at once (like in a background auto process). I wonder, if you "start all" on the app, and then immediately close the app (thinking that they all actually started), that the system is in process starting the workshops in small batches, and then gets cut off before that process completes.
I have not had this issue since I noticed the "small batch start" situation. Might be because I make sure to stay logged in for a good while and keep the window open, rather than letting it "go to sleep".
Just a thought.