Hello, I see the expert that was working with you opted out
I think what they mean is that one of the 'monitors' did not complete and pass, do you know which monitor it is, is it for the catalytic converter? It is possible for it to pass the visual test in California but not pass the monitor if the catalytic converter performance is slightly out of the allowed parameters, the computer may not run the monitor if this is the case.
The expert DJ gave you the correct procedure but it may not work sometimes, it is necessary to get the converter up to near maximum temperature to run the monitor, it's possible that the engine temperature may not come up to normal which can be caused by a bad thermostat. So make sure this is not the case.
You can also force the monitor to run, add a can of fuel treatment from the autoparts store, drive it on the highway at maximum speed limit for about 20 minutes, pull off, turn the key off and repeat then go have them check to see if it completed, you may want to consider getting a relatively inexpensive diagnostic code reader that can indicate which monitors did pass, these are about $150 and may come in handy later for diagnosing check engine lights, well worth the money, I think. It will cost you at least $100 to have the cat performance tested at the dealer.