Is this an MGCP gateway. If so, "show isdn active" will not show any calls because q.931 is backhauled to Callmanager. Also, "show voice call status" will show calls on interfaces other than ISDN such as FXO.
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...