It's possible that walls, people, or other entities are triggering the IR sensors on the sides of the board. To prevent this issue, make sure that there are four feet of free space on all sides whenever playing and that there are no large metal objects nearby. Return to the main menu and select "Options", then select "Calibrate Board" and follow the onscreen instructions. Make sure to follow the steps exactly and hold the board in the calibrating positions for the amount of the time the video that is play is telling you.
During the initial IR sensor calibration process ensure that you are standing away from the board and that you are motionless. When it is time to calibrate each individual IR sensor you will then be asked to stand on the board and will be shown some positions on the board to hold. Ensure that your entire foot is covering the lens of the particular IR sensor you are instructed to cover. Also ensure the board is facing the right direction. The buttons on the board should be on the left side of the board. Cover the whole sensor for the full count. Tony Hawk will say "Got it" when the timer is finishing. Continue to hold that board position until the button prompt to continue appears. Stepping off of the board before that will cause an error even after Tony Hawk says "Got it". You do not need to press a button to continue to move on to the next step. The calibration video will move on to the next step on its own.
If you still have issues with the calibration then try lowering the lights in the room. Sometimes bright lights can interfere with the IR sensors.
If trying the above does not resolve the issue then please contact the Activision customer service warranty website.