it looks like there are enough available keys and you should be able to grab one.
There should be a request key button on your purchase page. Can you find one?
Thanks for replying!
Normally there's a "claim steam key" section in the download page but I didn't see it on this download page? I have the same problem with some other games that provide steam keys and I didn't see the claim steam key section in the download page. Maybe it's itch.io's problem?
Do these resources help you with your problem?
No.. My problem is that there is no "claim steam key" section and no "get steam key" button in the download page