So you did Helseth's Blackmail and then Elysana's Robe quest? I was under the impression that you couldn't do both of them. Hrm...
You can do both of them
so long as you do them in that order. You can't do (or even receive) Helseth's quest after Elysana's, because
Spoiler The person whom Helseth wants to blackmail is killed by Elysana's robe, so obviously that messes the whole thing up.
(spoiler just in case someone's reading this thread who hasn't done the quests, for whatever reason)
I'm not sure what happens if you try to do it in the messy order given, but I doubt it results in anything good. Judging from the message you gave, it sounds like the game thinks you failed Helseth's quest (I've never failed that one so I don't know what the actual message would be), so no Barenziah quest, unfortunately.