if the user is not there then create your user and assign it to sudo group
root@google:~# useradd awan
root@google:~# passwd awan
------ if the user already there
root@google:~# usermod -a -G sudo awan
root@google:~# passwd awan
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
<<---- quick solution, change 'awan' to your user. and then reload the page and try to login