Problem to get acces using the root account

Hello, I have a strongbox. The root account is not shown in System/plataform menu. it only shows the fields to change the admin password I can access to TMOS using the account admin via SSH login as: admin Using keyboard-interactive authentication. Password: Last login: Wed Jan 14 17:30:55 2015 from 192.168.1.2 admin@(demo)(cfg-sync Standalone)(Active)(/Common)(tmos)

If I try to access using root account it shows me the following message: login as: root Using keyboard-interactive authentication. Password: Access denied Using keyboard-interactive authentication. Password: I tried to change the root password using this command: modify auth passowrd root it runs and aparently do its job, but if you try it you can't get access using the root account.

Any ideas to solve this problem?