Can anybody tell me what I'm doing wrong.  I have fed through the green block to the quadlock but I can't get it to fit in the hole were it goes.  Am I doing something wrong?

There are (at least) two styles of green connector, it looks like you have the wrong one

 

I think you need this: https://www.ebay.co.uk/itm/202080632933

 

You'll need to remove the pins from your existing connector and fit them to the new one.

Good man cheers!