Could you try from another browser? Make sure you're logged in to itch, request the key on that browser, open your email and verify it on that browser, and click to get the key again?
Make sure it's not in Incognito / Private mode etc, as that could stop itch from knowing it's still you.
Let me know if that works! If not please email me firstname.lastname@example.org and we can try to figure it out. If you know how to take screenshots you can email us what you're seeing as well.