Probably not broken. It has an auto-shutoff feature to save power if you forget about it.
The appliance shuts off automatically if no button is pressed for 20 minutes. To turn it back on, just press the on/off button. Your cooking program might be paused or canceled, so you may need to restart it.
If that didn't work: If it's shutting off randomly before 20 minutes, or if you see an error code, unplug it and check for other issues. Make sure the air vents on the back and top are not blocked and that you're not covering the air circulation openings during operation.
Heads up: Never leave the appliance unattended while it's in operation, even with the auto-shutoff. Always ensure you have control over the Airfryer during use.