Are you following the instructions in the ‘Weapon for FSX’ - User’s Manual on page 11? Make sure that your manual is the latest one dated VERSION: 06 JULY, 2011, because the instructions in the VERSION: 03 FEBUARY, 2011 are wrong.

Correct instructions to calibrate (VERSION: 06 JULY, 2011):
4. Press Ctrl + 9 or Ctrl + 0
5. Red calibration circle appears
6. Using Ctrl + Shift + 9 or Ctrl + Shift + 0 resize GREEN circle to match the red calibration circle
7. Red calibration circle automatically disappears in 2 sec

Incorrect instructions to calibrate (VERSION: 03 FEBUARY, 2011):
4. Press Ctrl + Shift + 9 or Ctrl + Shift + 0
5. Red calibration circle appears
6. Using Ctrl + 9 or Ctrl + 0 resize GREEN circle to match the red calibration circle
7. Red calibration circle automatically disappears in 2 sec

Hope this helps.

Mark