Since the obelisk changes every 2 hours, and only stays active for 20 minutes, it is most likely that there is no obelisk active at the time. The best way to find out when an obelisk is active is to open the Adventures interface and select the Minigames tab, from here players can select D&Ds from the drop down menu and see in real time when the next obelisk event will be active.
Might this be the problem?
We'll let you skip puzzles when you let us skip bosses. ~Foxxie