There could be many reasons for this but the most common is because the NOE module is not powering up correctly. The active light is an indication the module is powered up correctly and is connected to the back plain. You should try this NOE in another rack or an un-configured slot on the rack. If you have more then one Network option modules then remove all but the NOE in question. If this active Light does not illuminate then you will not be able to assign an IP address to the NOE.