Can't Claim a Purchase

[BKViper]

I purchased the New Year's Sale, which includes the Elephant Stable. When I go to your Inventory, I can see the Stable there, but the "Claim" button is grayed out.
I have enough free land space to accommodate it, even if it's 6x6, which I doubt it's that big.
Any other ideas why I can claim it?

 

[Empire Guard]

I had the same thing happen. I clicked on the grayed out claim button and a pop up message stated I could only have 1 event building active at the same time. I currently had the workshop active.