They didn't fire at all because there was a risk that they might have hit the ISS. SpaceX was operating under NASA's rules and NASA had a safety window where th

They didn't fire at all because there was a risk that they might have hit the ISS. SpaceX was operating under NASA's rules and NASA had a safety window where the Falcon 9 could/couldn't fire its second stage. The risk was almost certainly overstated, but NASA is understandably paranoid about things hitting the ISS.