I've just launched the lab within the last five minutes. It looks good from my end right now.
I'm assuming you may have connected to a rack that was having issues with the clean-up script that is supposed to run when the lab is exited.
Try now, if it continues to happen you can contact email@example.com.
My recommendation is if you do so, try and do a screen shot (yes, they'll want a full screenshots). Name of the lab, you're in, what browser you're using.
On your end, they'll ask you to clear out your browser cache and try again. Usually this works too.
*if the post above has answered the question, please mark the topic as solved.
**All "answers" and responses are offered "as is" and my opinion. There is no implied support or guarantee by the ITProTV team.