@Lancer
I once unlocked an expansion, but when I went to place it, it wasn't there. I sent in a ticket and they looked into my account.
Basically, there is (or was 11 months ago) a glitch that allowed me to place an additional expansion before I should have been able to, so when I unlocked the next one it didn't show because I had already hit my "expansion limit" as I was told. I had the same amount of expansions as other players, but I was able to place one earlier than I should have. So, it still worked out in the total of allowed/unlocked expansions.
Now, whether or not this is the same issue, I can't say. But that was my experience at least.