I have latest Source tree 3.1.3, when I try to add our Azure DevOps organization as Remote account I am getting following "Authentication failed Object reference not set to an instance of an object"error . I have used Username and PAT which has needed scope and access. Appreciate any help on how to resolve this???
Did you try the following order (i assume you did, but just to be on the safe side)
1: enter the old style url
2: Hit Refresh, this will show a popup
3: Create PAT in DevOps, and copy it
4: enter DevOps account e-mail (without the weird Microsoft prefix that sometimes shows up) as username and PAT as Password.
That should be enough to connect to DevOps