The Thermal Sensor on the Steam Thermoblock is defective. The Thermal Sensor monitors the temperature and sends the readings to the CPU. If the steam Thermoblock exceeds the required temperature to produce steam, then you may need to replace this part.
Visually check to see if the cable to the Thermal Sensor is broken, or contact pins are corroded. If so, replace/repair cable.
The Over-Temperature Protection is defective or blown. This fuse is a shut off mechanism when the Thermoblock exceeds the max temperature, or there is a power surge during the brew process. If this fuse is blown, it may indicate there is an underlying problem in the circuit.
Visually check the fuse and contact pins for corrosion. Also, check the OHMs reading to ensure there is a connection. It is recommended to replace the temperature sensor and fuse.
The steam Thermoblock is defective. Over time, the Thermoblock may become clogged with scale, preventing it from reaching the required temperature.
Replace the Thermoblock, sensors and fuses.
The Power Board is defective. The board is failing to receive the necessary signal that the coffee Thermoblock has reached the required temperature to initiate the brew process.
Replace the PCB; however, it is more economical to buy a new or refurbished machine.