When I click on the organization switcher button in the upper left I only see 13 of my orgs. I cannot see https://github.com/fugacious which is the org that I am trying to add.
All too often I figure out the issue after posting for help somewhere. There must be some quantum physics principle that explains that.
I double checked the settings and noticed that I did not grant CircleCI perms to the fugacious org. Problem solved. Thanks for the helpful text on https://circleci.com/account
Are you missing a GitHub organization? Check permissions.