These require that you have a certain feature set: IP Plus, IP/H323 (not sure about this one), or Enterprise Plus. In the future, you may want to consult the Software Advisor tool. It helps you to find IOS revisions and packages containing the features you want on the platform you have, and will advise you of RAM and flash requirements. It is linked from the Software Center page:
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...