Grohe push flush toilet cistern?

The flush on my cistern has decided to not cooperate anymore! I have opened it up to check it out. There are two tubes (one green , still attached, and one transparent, not attached) the transparent tube that attaches from the top push button flush, has come disconnected from the main unit in the cistern. I can see where and how the green tube connects ( it has not moved) but I am unable to see where the transparent tube has disconnected from (there is no visable prong/ or nipple, on the main unit that I can find in order for me to reconnect it to. Any ideas?