Ans: The sensor may not be communicating for any number of reasons. First check that your device is connected to the port specified in your program. If the port is correct, read the instructions here to view some basic information from your I2C sensor. Ensure your I2C address is the same as in your program. If you are still not receiving data, send an e-mail to our support team with the information you received from the explorer program mentioned on the page at the above link.
Ans: Read the instructions at here to change the I2C address of your device.