The Sims 3 Serial Key Problem (HUMBLE ORIGIN BUNDLE)

Hi!

So, I recently bought the humble origin bundle and got The Sims 3, along with the Late Night- and High-End Loft Stuff expansion packs. When I went to the official The Sims 3 page to register those games to my account, something odd happened. I logged in with my origin account, proceeding automatically to the register for a new game page. When I entered my serial key and other information, I was told I wasn't logged in anymore. Not understanding why I wasn't logged in anymore, I simply logged in again. Did the same thing as said before, and once again I was told I wasn't logged in. This process happened many times and after a while I gave up.

Later I tried registering my game again, but this time I wasn't sent to the register a new game page when I logged in. I thought I might have done something right earlier and went to check if the game was registered. It wasn't.

I figured I would try to register the game here " https://www.thesims3.com/registeragame.html " and so I did. 

Here's the weird part. It told me that my serial key was already used. How can that happen? No one but me has that serial key, and I didn't even get to register it to my account. What happened?

This happened to both the main game and the two expansion packs, probably because I tried all the serial keys several times the first time. Thing is that no one was logged in when I entered those keys. so why am I told they are already registered?