Unable to Connect to OnStar Message
If there is limited cellular coverage or the cellular network has reached maximum capacity, this message may come on. Push 
to try the call again or try again after driving a few miles into another cellular area.
See also:
Customer Assistance Offices (U.S. and Canada)
GMC encourages customers to call the toll-free number for assistance.
However, if a customer wishes to write or e-mail GMC, the letter should be addressed to:
United States
GMC Customer Assistance ...
Online Owner Center
Manage your vehicle (U.S.) at gmc.com. Click on “Owners,” then “Manage My GMC/Owners Login.”
Information and services customized for your specific vehicle — all in one convenient place.
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