New users unable to authenticate using AD

osTicket Version v1.9.14 (8b927a0)
Web Server Software Apache/2.4.7 (Ubuntu)
MySQL Version 5.5.50
PHP Version 5.5.9-1ubuntu4.19

I installed osticket in January and have been adding agents since then and all agents authenticate using AD. I also added a test user (username test.one) in January to test authentication. When adding a new user osticket would fetch the users details and fill in the blanks, such as email, first and last name.

Recently I wanted to add a new user, username test.two, and osticket does not fetch the users details from the AD. Even if I fill in the details myself (that is username, first and last name and email) the user cannot log in.

I have reinstalled the plugins HTTP Passthru Authentication and LDAP Authentication and Lookup (did that today) and I am still unable to get new users authenticate using AD.

If I delete an old user say test.one and try to add as an agent. Osticket will fetch the details from the AD as I am creating the agent and the agent is able to authenticate using the AD.

If I change the password of test.one from the AD the change is picked by osticket and only when the new password is entered is the agent able to log on. However I an unable to log on using test.two, even when I am sure of the password. 

There are no errors appearing in access.log but the systems log under the dashboard of osticket give the error -  Failed agent login attempt (test.two)

Username: test.two Attempts: 3