Caroma Verona dual flush cistern flush valve seal.

I have just repaced the seal at the bottom of the flush mechanism and the water does not dribble into the toilet bowl anymore. But now I can't get it to auto flush either half or full flush. It only flushes while you have your finger on the button. As soon as you remove the finger pressure the flushing stops. All I did was clean it in a weak bleach and replace the seal washer. The centre square tube that lifts the seal plunger does't seem to float after it is lifted like the other toilet. What have I done?
I have watched most of these Caroma YouTube videos: https://m.youtube.com/watch?v=yoYR7-SW8dQ

Mine has always done that, having to hold it down, from new.

used to be a trick that if you held the half flush button for the entire flush the cistern toggled into auto flush mode. If you held the full flush button down for the entire flush the cistern toggled into manual flush. I tried all this. Nothing changed this time.

plumbers?

Time to replace the inside parts. Which is really not worth it financially.
Husband is a plumber and we just bought a new cistern when ours did it.

Hmmph. There must a reason for the flush system not working now.

Fixed it! Took the mechanism out, pulled the new seal washer off. It seemedto be sitting okay but oilcaned hard against the plastic backng flange above the seal. This flange is not flat, it has a number of radial ridges.
Perhaps the seal should be floating more centrally in its groove than flipping either against the flange or cupping away from the flange. The cistern ocassionally hummed as a small leak fluttered the seal. Also I had installed the seal smooth side up and textured side down, ( I tried it both ways).
So I pulled the seal back off, smeared some palmolive dish washing liquid into the plastic groove and on the seal, to lubricate its depth of insertion into the groove. After coaxing the slimey seal to be an even diameter around the plastic flange, it seemed to be sitting a bit flatter.
Installed the flush mechanism into the cistern case and the "ball"cock arm into the valve with the brass pin. Turned the water back on and waited till the cistern filled with soapy bubbly water, and it Auto flushed, the centre square section flush tube floated until the flush was complete. Yay!