I am sorry that you have not been helped yet. I just came online and saw your question
There is not a reset, but there is a refresh procedure, which I have uploaded here for you. If it does not work, then there is an issue in the satellite receiver and will need to be diagnosed with GM factory level scan tool
To Reactivate/Refresh the XM Digital Radio Receiver, follow the steps below:
1. Tune radio to XM Channel 1 (Preview Channel), verify audio is heard. Tune to XM Channel 0 to obtain 8 digit XM radio ID. Allow 3-5 seconds for the text to page from XM RADIO ID to the actual ID number (press the clock button on the top-left bank of buttons if the display times out and returns to the date/time page). If Channel 0 cannot be tuned, connect the scan tool and navigate to the Module ID Information page and record the Radio ID. The Radio ID info is 8 alphanumeric characters.
2. Go to XM refresh website www.xmradio.com/oemrefresh and enter the 8 digit XM radio ID.
3. Park the vehicle where it may receive a clear satellite signal and have the vehicle running.
4. Tune radio to XM Channel 1 (Preview Channel).
5. The process may take up to 20 minutes to receive the complete XM. Channel list Notice: The refresh signal will be sent for 3 hours. The vehicle must be powered up within the 3 hour window to receive the refresh signal.
6. Verify the channels in the current channel lineup are available, to verify if the activation is complete. Notice: Occasionally XM will run an expanded preview mode where more than the normal preview channels will be heard (holidays, promotions, etc.) If the radio is also intended to receive data services (e.g. NavTraffic, local forecast, etc.), verify these authorized services are also received. If the channels are not available, tune back to XM. Channel 1 and continue the refresh.