Unable to connect from Sourcetree to my remote repository in Bitbucket

[name withheld by request]

I am unable to connect from Sourcetree to my remote repository in Bitbucket and I want you to help me please.

In my bitbucket account I have created a repository. I then open my Sourcetree (version 3.4.6) and try to add a connection to that repository. I go via this route: New tab -> remote -> add an account -> Edit hosting account -> hosting service=bitbucket, preferred protocol=HTTPS, authentication=basic, username=[redacted], and press "refresh password". I then get the error message "Authentication failed Unexpected character encountered while parsing value: Y. Path ", line 0, position 0.".

Please tell me how to cure this problem. My machine uses Windows 10, I am using Bitbucket.org, my Sourcetree version is 3.4.6, I dont know how to attach a screenshot. I note that previous reports of this error have been marked as "fixed" even though they haven't so I must request that you actually answer this one please.