Even though there may be a current maintenance contract the license may not have been updated. Call support or your sales person and they can get your licensing updated. Once the licensing has been updated you can reactivate your server.
Yep - Kenyon - is correct.
This is most probably just something that needs to be fixed / updated with your license on the licensing server back-end.
Getting in touch with support would be the first thing to do here (they may request your activation credentials, just so that they can confirm the problem you're seeing locally & can then work with the licensing folks to get this resolved).