Please wait until your existing giveaways are finished and received before creating additional give

Chances are they are all taken by your seven item giveaway.

The more you do, the more you can make later. I can make a couple of hundred, but I also made several hundred in the last few years.

You are assigned "slots" to create GAs, starting with 2. The more GAs you finish (marked as "received"; based on number, not value), the more you will be given.

Depending on how many giveaways have been marked as received, you are limited as to how many you can make. I believe you start at 3 then it goes up from there. Me, for example, can make 20 total. Once I have 20 I can't make another one till one I have made finishes and has been marked as received.

Exactly what everybody else said, except every time you cancelled a GA you lose that slot.

As you have limited slots, I'd recommend making your giveaways shorter.
Your current 7 copy giveaway runs for more than 3 weeks!

For every 3 games sent, you unlock an additional slot. If you send tons of stuff, you earn more slots....
For someone like me... whose sent nearly 2000 games, I've unlocked over 600 slots :)

All users start with three slots. With every three successful giveaways, you gain another slot. With every deleted giveaway and every negative feedback, you lose one slot.

I have about 5 giveaways that the people still haven't marked as received, so I can't make more. It's pissing me off.

number of slots = initial 3 + [sent with successfully received mark /3] - running(temporary) - deleted(permanent) - not received(semi-permanent)

Keohookalani and jatan are right. But if you have X keys and you want to make a train with X wagons (supposing that X is way bigger than your number slots) you can open a new ticket asking gently the support if they can add you the number of slots you need to make your train/megapuzzle/event/whatever. They'll answer to you very rapidly and 99% will give you the slots you need ;)

Thanks everyone i think i just have to wait !