Hi SnailChan!
Someone else also had a problem where the button to get the steam key wasn't showing at all. She did say she eventually got it to show up, but never said how. We are showing 60 unclaimed Steam Keys so it should be possible download them.
Unfortunately, buttons appearing on our page (or not appearing) is outside our control so I will have to contact Itch.io support to see if they have any suggestions. That said, you may wish to do the same as it could be an account specific problem rather than an issue with our page. I can see that keys have been claimed very recently, so I know the button is showing up properly for some people. We may get a response faster if we both reach out about it.
I'll be sure to let you know as soon as I hear something.
Thank you for letting us know about the problem!
~Esh