Had a Gold Star ready for Tartarus... Clicked on Descend for Level 70, a window pops up asking if you want to descend to Tartarus. I click "YES" then the menu disappears, but it doesn't take me to Tartarus. I'm just left standing in front of the entrance like nothing happened. Went back into the menu and the Gold Star was "used" / gone. Happened at around 5:45 UTC. Jan.8th., and again on January 16th. It has happened to me a handful of times in the past as well. It does it with both star types, white and gold.