Upon investigation, the system that is installed is improperly sized towards environment. There’s not enough make up air to operate this type of on-demand water heater system. The system needs more volume and turn this caused safety feature to lock the system out due to not enough make up air. The flame vapor sensor is out at this time unfortunately due to the confined space even if it is replaced, this will not permanently fix the problem. This water heater has a maximum output for a standard sized home with up to three bathrooms and it is installed in an application with one bathroom and less than 600 ft.² system is oversized for its application.