Hello. I am using Unity 2017.1f3 and having issues with your asset. Following your documention exactly, I click the button to get my API token, the trello website opens and I click "allow", I copy the API token and paste it back into the Unity setup field, and then click authenticate token. Each time the authentication fails. I had recently also purchased a competing product on the asset store that does it slightly differently, I get my own API key and API token and paste those into the other asset, and that one worked fine. 

Thanks for letting me know, and following up with a fix via email!

I've patched in your fix in 1.0.2 which is live now on itch, and should be live on the asset store within the next week. :)