I've uncovered the Wizard's Skull a couple of times now, but didn't get the achievement when I hit send score button. Do you have to get to the treasure chest too to get the achievement? Or is there a problem with the game?

I'm pretty sure you don't have to reach the treasure for it to count. I can't remember if you need to send the score or not for it to work, but if it's not awarding for you either way it's probably worth making a bug report about it. Could be related to the server issues or something else, but anyway they can look into it with a report.

Maybe a silly question, but you're uncovering the whole skull, right? It takes up two tiles and you need to uncover both

That may be the problem because it looked like it was all uncovered in just one square to me. It's the skull with the horns right? I'll just uncover everything around it next time it pops up.

Thank you both. I finally got the thing. I was looking at a picture of the wrong skull that I thought was it.

Glad you got it figured out :)