@Ponderable saidSorry, my error. A login is required now to go beyond a depth of 3 moves. This was introduced due a recent incident when a bot was attempting to "scrape" the entire game explorer database. (For AI training, perhaps.)
Looks like you can only "explore" up to four three half moves now.
I was aksed to register.
So do I need a different registration? If so it would have been a nice move to announce that befirehand.
Anyway, I messed up - now fixed - you shouldn't be seeing that prompt.