Authentication not working to VSO

I just updated SourceTree to v 1.9.6.1 and am unable to log in to Visual Studio Online repositories. It was working previously.

I can connect and pull with the same credentials using Visual Studio's built-in Team Explorer - so I know the credentials are correct. I deleted and added the saved password in Tools > Options > Authentication, but it didn't fix anything.

Also tried: closing Visual Studio to make sure it wasn't a file access issues as seen in another issue. Updated the embedded version of git.

Any suggestions?

Here's the error I'm getting:
git -c diff.mnemonicprefix=false -c core.quotepath=false fetch origin
fatal: Authentication failed for 'https://xxx.visualstudio.com/DefaultCollection/_git/xxx/'
Completed with errors, see above.