Try this:
-stop jenkins
- go and edit /var/lib/jenkins/config.xml
- Change <useSecurity>true</useSecurity> to false
- Restart Jenkins: sudo service jenkins restart
- Navigate to the Jenkins dashboard to the "Configure Security" option you likely used before. This time, setup security the same as before, BUT set it to allow anyone to do anything, and allow user signup.
- Go to www.yoursite.com/securityRealm/addUser and create a user
- Then go change allow anyone to do anything to whatever you actually want users to be able to do. In my case, it is allow logged in users to do anything.