As stated in the firmware's own README here:
Quick Information
[...]
- Added protection of the heaters if you do not print after 30 minutes on. It is important that the host gives the command M530 S1 for the start and M530 for the stop.
you'll need to add M530 S1 to your start and M530 S0 to your end GCODE, either in your slicer or in OctoPrint's GCODE Scripts. Otherwise the firmware's "heater protection" will trigger and disable your heaters, causing cold extrusion errors and your print to fail.