If you've completely loosened the truss-rod to the point where it's loose and the string height is too low still, it's possible the guitar may be defective. It may eve have a slight "back-bow".
If it was an older guitar, there are things to try, like putting heavier gauge strings on to increase the neck tension, that you can try. There's also more extreme things you can do to fix this, but they involve taking the neck off and, personally, I would recommend you talk to a luthier for this sort of stuff.
However, given it's a brand new guitar, I would take it back to where you bought it and either ask for a replacement or for them to fix it to your satisfaction (or get a refund and buy a new one from somewhere else).
However, before you do that, leave the guitar with the truss rod loosened for a few days and then recheck it. They can take quite a time to respond if the truss rod was overtightened.
Cheers,
Keith