Charactermancer stuck at start (DnD 5e sheet)

One of my players was doing his levelup and the sheet got stuck at the very beginning. I haven't tried from a more powerful computer but this shouldn't be happening (I have tried using a popup sheet and reloading the page). It won't even let me exit the charactermancer. What can I do?

Sounds similar to an issue i had. I think the only way to cancel was to go back to the first intro page then cancel. The charactermancer doesn't work without access to the GM resources. Once my GM provided access it was OK. It would be good if there was a message feeding this back. It could be helped by a default message saying "accessing GM resources" that then gets overwritten. At least that would be a clue as to why its stuck.

Thank you for the replies. I cancelled in the way Analyzer said and it helped, but I couldn't launch the charactermancer again or else it just went back to the same state. But then I tried Mel's suggestion of going back and hitting cancel (I had to start the charamancer up again) and the next time everything loaded perfectly. As for the reason, I had told the player to levelup but I hadn't realized that I wasn't sharing my compendium with them (having only 5 slots is the worst), so it seems it bugged during that moment. Thank you both!!