If upon logging into your DirectAdmin panel you see a License Expired! error and are sure that it is active, you can try manually re-syncing your license. This is done in two steps:
# /usr/local/directadmin/scripts/getLicense.sh <cid> <lic_id>
Where cid is your DirectAdmin client ID and lic_id is your license ID. You will need to ask NDC Host for one or both of these if you do not already have them. After running the above command, restart DirectAdmin:
# /etc/init.d/directadmin restart
That's it! Refresh the DirectAdmin admin page if you've already logged in or try logging in once more.