How long are you waiting at the light during the day? Check with the city transportation department what the maximum time should be for the light to change and report how long you've had to wait. The sensors are adjustable for sensitivity and they should be able to pick up your bike (and appear to do so at night). If they consistently detect you at night they should also do so during the day. But of course there will be a longer delay during the day for the light to change if there's lots of traffic on the cross street.