When I pull, I get this window

Even though I enter correct username and password, it keeps popping out. The pull doesn't complete, this is the error:
git -c diff.mnemonicprefix=false -c core.quotepath=false fetch origin
fatal: HttpRequestException encountered.
An error occurred while sending the request.
remote: Invalid username or password.
fatal: Authentication failed
I am able to pull through command line, but not through the sourcetree interface. Please help!