Unable to add Bitbucket Server repositories

Created by: KattMingMing

After adding an External Service for Bitbucket, repositories are unable to clone.

The list of repositories appears in the repositories view, but every repository shows an error that it is unreachable. Below is a sample error:

The remote repository is unreachable. Logs follow.
repo not found (name=XXX url=XXX.git notfound=false) because exit status 128 (output follows)
fatal: Authentication failed for 'XXX.git/'