How can you tell if a motor driver chip is defective?
Replace it with one that is working if they are on pins. So you know the newly inserted is working and if motor does not turn you are using wrong configuration or something in wiring of motor is bad, not connected,...
Note that extruder motors normally only work if extruder is hot or cold extrusion is enabled (M302 S1). Also check eeprom if steps per mm is set there.