Bitbucket Branch Source Plugin versions 2.2.x cannot select a repository that you are a contributor to. It only loads repositories from teams you're a member of, or individual repos that you are the Owner of. But if you are a Contributor to a private, personal Bitbucket repo the Branch Source Plugin will not populate it in the dropdown list.
The Relevant code appears to be here:
My Jenkins install is covered in warnings and errors because I can't update anything if I can't build the repositories I need to on the update.