The H-Series does have a Thermostat function that can cause this behavior.
The Thermostat Mode is a feature on the H-Series fireplaces that is used to maintain a specific room temperature.
You can determine if the fireplace is in the Thermostat mode when it reads 'on' next to the thermometer icon located in the top left corner of the remote control is display.
In the example above, the fireplace would have turned off because the thermostatic temperature, located in the top right, met the room temperature located in the center of the display.
An typical example for use would be if the room temperature was originally 62 degrees, and the thermostat mode is set to 69 degrees. In this scenario the fireplace will shut off once the room reaches 69 degrees. How long it takes to for the fireplace to shut down is dependent on the size of the room and where the remote is located relative to the fireplace.
To turn off the the Thermostat mode press the thermostat button 2 more times until the temperature is no longer displayed.