Troubleshooting a Fogatti Tankless Water Heater:

Problem 1: Monitoring screen not responding but unit is on

• First, test the DC voltage using a multimeter. 

- Connect Voltage Meter to the Board Connection Cable

- Connect Voltage Meter to Controller Connection

When you turn the unit to ON you should be able to hear a 'Metallic Click" sound coming from the board. 

Problem 2: Monitoring screen is on but no response from the water heater

• This could be related to a faulty Water Flow Sensor. To check the sensor, release the pressure by undoing the pressure release valve and blowing compressed air into it. If the air flow does not ignite the exhaust and turn on the sensor, it should be replaced. A working sensor will ignite the exhaust and respond to the compressed air flow.
  
  
• Additionally, check the plumbing to see if there is any water flow stress on the system.
  
  

Since you already checked the voltage and and water pressure on your Fogatti Tankless Water Heater, werecommend checking the gas pressure.