Make sure the distance from the transmitter ( on your fork) to the receiver (handlebar mounted computer) is within the distance recommended by the manual (usually no more than 18" - 24"). Also, remove the battery from the transmitter and do a light scrape on the top of the battery terminal. Sometimes these things (even new) sit in inventory somewhere for quite a long time. Before you do that though, rotate the wheel and listen for a small click sound every time the magnet passes the transmitter. If you here nothing than you need to adjust magnet and/or check that battery as described above. Or for 3-6 bucks you could just replace the battery without messing with it.