Understanding the lid mechanism: First image. When the button on the handle is pressed (yellow arrow) the two latches on each side of the lid (green arrow) should retract from the two holes (orange arrow) allowing the sprung loaded lid to open.

The second image shows an enlargement of the hinge area. When the handle button is pressed a small round plastic pin (blue arrow) pokes out and, when the lid is closed, presses on a rectangular pin in the lid (red arrow). This rectangular pin should retract the latches.