So far as i can tell this is an unusual problem with onStar. I'm posting here so that it's recorded for anyone in the future who needs the information.
On delivery, when pressing my Volt's onStar button to set up the account, the system said "OnStar has not been activated. Press the blue button to connect to onStar." On pressing the button again, "Dialing onStar. Beep...beep...beep...beep...beep. Unable to connect to onStar, try again later." The same symptoms recurred several times in different locations during the week. OnStar technical was unable to contact the car either and said to bring to dealer.
Dealer had the Volt for two days. The transcript of the service record is:
Customer states unable to activate onStar at time of purchase and now when attempting to contact system beeps only as if dialing then unable to connect. Customer has contacted OnStar technical support by phone and was advised to take vehicle to dealer. Check and advise.
Verified customer complaint. Perform base check on vehicle and found both emergency button and blue onStar button both get no connection to onStar errors. Pressing white button gets menu items and will receive commands. No codes I in VCIM. Called TAC case # xxx. Will wait for TAC to return call with OnStar specialist.
Instructed to continue with PIC4310F. Gathered information as per PIC. Also install EL-49903 into system. Still has same issues with system.
Disconnected VCIM and let sit 3 minutes. Reconnected system. Attempted to connect to onStar (blue button). Vehicle connects and location of vehicle is given.
Called TAC for further instructions. Power cycle telematics communication interface control module. Connect to onStar and give location w blue button. System did connect. Performed verification phone call with TAC. Case Closed. Customer will need to setup through blue button and perform digit dial.
My Volt advisor says that there was a module in the onStar locked up and possibly with a power-related code. So I pick up the car and set up through the blue button. I buy 60 minutes of phone time and the download to my car of those minutes fails. Transfer to onStar tech support. About ten minutes of testing etc, then the minutes download. They were kind enough to give me a free 100 minutes by way of apology for the trouble, which was quite kind.
I get home, log in to myVolt.com (finally). The web site can't connect to the car. Neither can the iPhone application. I go to the car, can't phone out from the car with onStar.
Next day, drive to work. I can phone out form the car. I can connect to onStar advisor and tech support. They can't find any issues. iPhone app still not connecting. I delete the iPhone app, re-install it, can now get car info into the iPhone. Connecting at home with myVolt failed, but with iPhone succeeded. Later tonight, myVolt connects correctly.
So I can't call it quite closed yet, but it's likely that this has been fixed.