Hi there,
Sorry to hear about that. I can confirm that you have bought the game and should be able to download it. I believe that should be a problem on itch end's. I'd suggest for you to try this:
https://itch-io.cdn.ampproject.org/v/s/itch.io/docs/general/faq.amp?amp_js_v=0.1...
Or even contact itch support directly. Or try to find the email you got with the purchase and try that link?
If nothing works, let me know that I can send you a new key via email. But I'm not on my PC right now.