When we are trying to access any branches from bitbucket sourcetree we are not able to access and giving an alert to provide login credentials. Once after providing valid credentials also we are getting the same can you please help on the same.
Please make sure you are running Sourcetree 3.0.12 and preferably install Git 2.19.2 and configure Sourcetree to use that install in its Tools/Options/Git tab as a System Git.
There have been a few issues with the Git Credential Manager that ships with Git for Windows recently, v1.18.3 which is included in Git 2.19.2 seems to be much better.
Additionally if you are using Mercurial, Sourcetree 3.0.12 includes updates to cope with TLS 1.2 and the recent removal of TLS 1/1.1 from Bitbucket.