Overheating, fan does not seem to kick on

Hi, my car has been sitting on the drive since November and late January I went out to it to see if it was alright to go through and mot, but then it started to overheat and flash on the red line on the temperature gauge. I’ve changed the thermostat and the sensor as the fan doesn’t seem to kick in. It uses so much coolant but I don’t see any liquid dripping from the bottom of the car. I wonder if you could give me any advice on what it could have been. My old man knows a fair bit about cars but he doesn’t see why the fan one kick, he suggest it could be the fan resistor but still unsure.