I get this error; 

This download page is owned by another account on itch.io, you do not have access to it. If you think this is a mistake, please get in touch with support

But I do get the email with downloadlink for nimble, yet can't download it using that.

I recommend you get in touch with Itch.io support as it suggests. I can’t help you with this myself, unfortunately. My guess is you’ve made another Itch account at one point and you’re logged into the wrong account.