Then it would be best to take things in small steps.
This is what my code would show.
Take this project, hit the COPY THIS APP button and flash it to your device.
Then unplug the device, plug your DHT22 sensor directly next to the Argon aligning the sensor pins with D2 (-) D3 (out) D4 (+)
When you then power up the device again and connect it to your computer via USB and watch the Serial output via particle serial monitor --follow you should see valid readings.