Unable to purchase Tier 10 of Conquest Ascension

I was getting that same problem, but try searching for energy via Conquest. Click on Energy and when it asks for you to find more energy options, it should present to you the option in the store for the Conquest Ascension. (Either that, or click on the Conquest Ascension icon on the right hand of the screen). I can't remember exactly how I got around it, but I just could never get it to the load in the In-Game Store. It was just give me the spinning circle of death.