Stopped working for me too, switched to the Duome tree. One problem however is that there is a desync in terms of progress and what the tree looks like. I used www-internal to get the next skill to 5 crowns, which is what it shows on the Duome tree, but what it actually was was 0 crowns. I used the old apk app version to test it to one crown, but the Duome tree still said 5 crowns. Changing the url to do the test for the skill also works, and immediately syncs up with the app, but the Duome tree still doesn't update.
I'm gonna continue doing that to get it to the five crowns I used to have, but I hope this desync doesn't mean that the Duome tree stops updating altogether and leaves the next two skills blank forever.
EDIT:
The Duome tree was down for a bit and now back up. I tested it by doing a legendary lesson for an early skill, and it seems to update fine now.