@Simas, I had that issue too. After setting the sensor to poll mode and starting the calibration manually, everything worked fine with Rob's library.
You can find the sketches to do that here on the forum and in my repo (the SetToPolling and Calibrate sketches).
Edit: Also make sure the sensor is connected to pin 2 and 3. If, after trying the above, you still get the 0 readings, try switching the wires, there was some confusing about Tx and Rx. And give it a bit of time. After it's connected to power, the sensor needs about 5 seconds before it measures correctly.