Geberit impuls280, please flush

I'm not in the profession of plumbing or any trade for that matter just a "do it yourself" kind of person and a bad one at that.
I'm having trouble with this particular fill and flush valve (geberit impulse280). No flush after pushing either of the half moon buttons all the way down. I don't know really what I'm looking for and wouldn't be able to spot an error in the system if I saw one.
Can anyone give me a little help in troubleshooting this. What I should be looking for or perhaps a link to an explanation of this partiular flush system to better understand it.
Thanks.

Hello

I am just having the same problem and I have just seen your post. Did you get any replies to your question? were you able to fix the problem? If so, could you please let me know what you did.

Many thanks

I had the same problem and managed to fix it after the flush valve was inspected.

Geberit Flush Valve unable to push water out of the cistern. Problem was due to the four protuding latches from the lower plunger mechanism unable to latch into the upper piston mechanism. Their location is visible approximately 3 inches from the top of the flush valve unit. Two broken bits from this latch were found loose in the cistern. This locking of latches were glued up using a hardener providing a temporary solution.