My Distance Sensor doesn't detect objects that are very near.

The Distance Sensor measures distance to an object or surface using ultrasound. The sensor works by sending out high frequency sound waves that bounce off any object in range, and measuring how long it takes the sound to return to the sensor. It cn detect objects between 50-2000 mm +/- 20 mm. So it might not detect the object if you are too near or two far. Probably a good idea to stay at 7mm or above!

I have attached the technical specification sheet here if you want to find out more about the great sensor.