MyChevy app broken after OnStar board replacement

I have a 2024 Blazer EV.  The GPS went out, and the OnStar board needed to be replaced.  This was done on 12/11/2025.  I was very happy as the GPS and navigation were restored, and the vehicle was working perfectly.  However, the new board rendered the MyChevrolet app useless.  The app state my vehicle is connected but nothing works.  It will not update. The last update was 4 days ago.  In fact, the app states the milage on the car is 11,026 miles.  this is the exact milage recorded by the dealer when I dropped the car off.  The milage out was 11,027.  The board fixed the car but not broke the app.

I have spent an hour with Chevy EV concierge, and they were not able to resolve the problem and instructed me to call the dealer.  I called the dealer, and they told me it was an OnStar problem that they could fix.  I called OnStar and spent an hour trying things only to find out they could not resolve the problem.  Everything seemed to be connected on their end.  I was given a case number and told they would be in touch.

Chevy Ev concierge called me back to tell me they ran a higher-level diagnostic and got a lot of SMS errors, and I should go back to the dealer.  I now have another day at the dealership and no confidence that anyone will be able to fix the problem.

I should be a simple issue.  If a board goes bad and gets replace, the problem gets fixed and is does not create another problem.