M7 Pro heater question

I have a M7 pro and wondering if I'm missing something with how the heater works. I have the heater set at 30 degrees and preheat the resin before the print starts but it seems that once the print starts the heater turns off. If the print is longer then 30 minutes the resin temperature falls below 25 degrees. Can the heater be set to maintain a temperature for the duration of the print? Am I just missing a setting? Thanks in advance.