I\'m using the github oauth plugin for our logins but for all of our users in the Organisation I get an error:
Access Denied
is missing the Ov
I had the same problem here, but it affected only some users, not all of them. Anyway, you should check public organization membership : documentation of the plugin states that "You have to be a public member of the organization for the authorization to work correctly." (https://wiki.jenkins-ci.org/display/JENKINS/Github+OAuth+Plugin).
Follow instructions from GitHub (https://help.github.com/articles/publicizing-or-hiding-organization-membership/) in order to make organization membership public, and this might fix your issue.