You'd need to give a few more details to work out what the problem is exactly, but the first thing that comes to mind is that either your account hasn't been approved yet, or has been suspended.
In both cases, you should be able to login to your Adsense account and check for alerts on the top right corner of the home screen.
New accounts are usually subject to a two-step approval process, so it could just be that your account has yet to be approved. This often takes around a week or so.
If your account is suspended, and you're not a "big important publisher" on their network, then it's not uncommon not to receive a detailed explanation for account suspension - but you will receive an automated email and an alert on your Adsense dashboard.
