I have been getting a similar message with a similar problem. I cannot download any games through Ignite currently and I've never had this problem before. I've downloaded/re-downloaded AVA a few times through Ignite with no problems except for the most recent time when I went to re-download AVA.
Now, when I hit download, after a few seconds, it says, "Unexpected error has occurred while Ignite was downloading this game." It's very irritating and I have yet to find a solution.
The only thing you can do is download AVA through Steam but the problem for me with doing that, is that I can then only play on one account. I normally play on multiple accounts.
I have also sent in a support ticket and did get a response with some steps, (Most of which I've already done and stated that I did them in the support ticket) and really the only new step that they gave me was to update windows. I installed all of the updates I had available, but it didn't change anything and the same message still appeared.
Anyways, good luck finding a solution and if you do, please post it here. Hopefully, someone can help me, you, and anyone else.