Right, the same thing happened to me.
I asked support about it, as the information is contradictory - saying they need "posting authority" but then asking for the "active key".
I asked support about it, mentioning my security concerns. This is the only explanation so far of why I would need to enter my private active key. And of course, it doesn't make any sense - the posting key is for posting.
Yep, they keep asking for active key, the posting key seems not to work at all...
So the active key would give them access to the funds in my account, which I'm not willing to do. I'm beginning to have my doubts about the legitimacy of @threespeak.