I just want to inform about an issue.
I was creating a board within Bitbucket and I wasn't able to view it, showing the message 'Board not found' and a text to log in into Trello, that opens a new window and closes it instantly.
After trying to do it in an incognito tab, thinking that it was because some plugin, with the same result, I realised that I didn't have a password in Trello (I log in with my Google account). So I set the password on the Trello account, log out and enter with the password instead of the Google account, and it works.
Hope it helps.