It’s easy. Just squeeze the bin itself across the top diameter and you will notice that the pin lugs in the bin flex out a bit. Slot one pin off the lid into one side lug and then push the other in while squeezing the bin itself. Really easy. No brute force required
Having looked at all the suggestions, I wondered what made the lid come off so easily as mine did? Most said it was banged against something or knocked. So I realised that knocking it must do something. You know what , it does. It compresses the round plastic circle into an oval shape. So I compressed my bin by squeezing it with my fingers across the open top at 90 degrees to the latch and hinge pin. Guess what? The hinge pin holes flex slightly outwards allowing you to ease the bin lid pins back into place. Easy peasy . No brute force, no danger of the pins breaking. Just squeeze across the diameter of the top of the bin with one pin hinge of the lid in its hole and the other will slot into place, Voila!