Account unable to login

Hi all, I have this testuser account which doesn't seem to be able to login. It's in the same Windows AD group as other account and it have admin rights on F5. Other windows account is able to login except this one.

Looking though the logs under /var/log/secure, what does tty=(unknown) means ?

Feb  7 06:50:41 Host1 warning httpd[4325]: pam_unix(httpd:auth): check pass; user unknown
Feb  7 06:50:41 Host1 notice httpd[4325]: pam_unix(httpd:auth): authentication failure; logname= uid=48 euid=48 tty= ruser= rhost=172.20.0.1 

Feb  7 06:50:44 Host1 info httpd(pam_audit)[4325]: User=testuser tty=(unknown) host=172.20.0.1 failed to login after 1 attempts (start="Tue Feb  7 06:50:41 2017" end="Tue Feb  7 06:50:44 2017").

Feb  7 06:50:44 Host1 info httpd(pam_audit)[4325]: 01070417:6: AUDIT - user testuser - RAW: httpd(pam_audit): User=testuser tty=(unknown) host=172.20.0.1 failed to login after 1 attempts (start="Tue Feb  7 06:50:41 2017" end="Tue Feb  7 06:50:44 2017").

Feb  7 06:51:09 Host1 warning httpd[4325]: pam_unix(httpd:auth): check pass; user unknown
Feb  7 06:51:09 Host1 notice httpd[4325]: pam_unix(httpd:auth): authentication failure; logname= uid=48 euid=48 tty= ruser= rhost=172.20.0.1 

Feb  7 06:51:12 Host1 err httpd[4325]: [error] [client 172.20.0.1] AUTHCACHE PAM: user 'testuser.itrs.local' - not authenticated: Authentication failure, referer: https://172.20.34.3/tmui/login.jsp?msgcode=1&
Feb  7 06:51:12 Host1 info httpd(pam_audit)[4325]: User=testuser.itrs.local tty=(unknown) host=172.20.0.1 failed to login after 1 attempts (start="Tue Feb  7 06:51:09 2017" end="Tue Feb  7 06:51:12 2017").

Feb  7 06:51:12 Host1 info httpd(pam_audit)[4325]: 01070417:6: AUDIT - user testuser.itrs.local - RAW: httpd(pam_audit): User=testuser.itrs.local tty=(unknown) host=172.20.0.1 failed to login after 1 attempts (start="Tue Feb  7 06:51:09 2017" end="Tue Feb  7 06:51:12 2017").

Feb  7 06:51:48 Host1 warning httpd[4325]: pam_unix(httpd:auth): check pass; user unknown

Feb  7 06:51:48 Host1 notice httpd[4325]: pam_unix(httpd:auth): authentication failure; logname= uid=48 euid=48 tty= ruser= rhost=172.20.0.1