My settings for max Distance and  Altitude go back to default which is o. I fly in Canadian air space in G airspace. What can I do?

Hi, we're sorry to know about the situation. I would like to ask if you're a mobile device when using the Phantom 4 Pro? The Maximum Flight Altitude and Max distance shouldn't reset to 0 meters as this can only be set for minimum 15m only. I would recommend providing us the screenshot of this problem and change the location to isolate the problem. Please keep us posted on the latest progress. Thank you for your support.

It sounds like you are trying to reset them in the app without being connected to the drone.
Those settings are stored in the drone itself.
You can't change them unless the app is connected to the drone.