Can't calibrate line follower[SOLVED]

After connecting through VNC and clicking “Line Follower Calibration” on the desktop, first I got a terminal window with warning message of <Xlib: extension “RANDR” missing on display “:1.0”>, the application still could run.

Then I click “Set Black Line Values”, instead of displaying values on the bottom of the window, it displays lists of values(-1,-1,-1,-1,-1) on a new terminal window and the application hang.

The system software is 2016.06.15_Dexter_Industries_jessie.rar, I didn’t add any extra software yet.
The GoPiGo and line follower were newly bought.

What port is the Line Follower plugged into? When you plug the line follower in, what are you seeing with the LED’s?

The line follower is connected to left top port which is near the left LED on the GoPiGo main board.
On the line follower, I see the right LED is steady green, the left LED is flashing red.

BTW, the Pi is Raspberry Pi 3.

Now I noticed that I connected to the wrong port, thanks for your help and issue fixed:)

Great, glad we got it solved. The Line follower goes on the I2C port, just in case anyone is having the same issue!