What version of the manager are you running? Licensing was removed for everything except for NAC in 6.0.3.x --quite some time ago. If you are running a version older than this I highly recommend upgrading.
If upgrading is not an option you will need to contact the licensing department via email to request a new license. The license file contains dates within it that should be a number of years. You can rename the file to .zip and open it up to verify what dates are on the license file.