I am having this error over and over,
Signing in, a white windows pops up completely empy.
Tried changed delete account and create it again, didn't work.
tried change protocol HTTPs to SSH, didn't work.
Tried re-install SourceTree, didn't work.
SSH key is the same than the one in Bitbucket.
Thanks for the detailed description and the screenshots.
When you re-installed Sourcetree, did you make sure to wipe the Sourcetree preferences? You can find the instructions here. Can you try that and let us know if it worked for you?
Also, for troubleshooting purposes, can you tell us if you're getting any issues when trying HTTPS instead of SSH?