On Fri, 2 Oct 2015 10:13:32 +0630, John Smith wrote:

Can anyone explain why a flapper which was not leaking leaks after
cleaning? Much appreciated.

Did you also clean the seat (the part it rests on when it's shut). Clean
that too! Of that seat is worn or corroded, you may need to replace
that too. That requires removal of the toilet tank. Not a hard job, but
time consuming, and will probably require new tank to bowl bolts and
rubber seals as well.

I assume you checked to make sure the chain is not holding it up a
little, or some other object in the way....