If you're still getting that error even after you come back to the car for a new journey then get it booked in with your dealer.
Don't let them fob you off that its just not met its conditions for it to auto stop start. If it hasn't met the conditions you just get the little A with a line through it as mentioned above, this is just a little notification.
An ERROR is indicating that there is a problem, you wouldn't get an error if its too cold to auto stop start, you'd just get the little A with a line through it as a notification.
If you're still suffering the problem I'd get a photograph or two of the error you're getting displayed and then get it booked in, so you have the proof it was happening even if it "magically resolves itself" at the dealership. Don't let them fob you off, awful customer service that they just said that.