I am sure you have set significant digits, incoming CSS on GW correctly and destination-phone is registered to ccm. If not ideally you should get error-message from CCM rather then fast busy tone, but you've not specified CCM Version and there are bugs in CCM 5.0 which prevents message from CCM so I thougt of mentioning it.
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...