The thermistor wires have broken, you will need a new thermistor. When you fit the new thermistor only just pinch it with that screw, too tight will break the wires and need another new thermistor. Keep spare thermistors and heaters (the part connected to the red wires) in your printer toolbox, they are cheap and easily broken.
I’m not sure of the exact model you have but here’s a video that might help show how it’s put together and where to order parts on places like Amazon or ali express etc…