Do traffic lights sometimes not work when you’re cycling?

Try having a look at this video from the US, with the same basic problem and solution, it works here in Dublin too:

The loops are usually square or rectangular here in Dublin.

Some traffic lights also have what look like a camera at the top of the the traffic lights. This is a sensor, when it is triggered a small red light should come on — if it is not lit up, and the road is clear, try to move around just behind the stop line to trigger it.