It is true that cancellation of ticket may not be possible once 24 hrs is
crossed. Now, they could get rid by giving excuse that the page on the internet
is not work during that time. Can you try the same and see whether you get the
prompt or warning msg.
If you dont get even now, than it is the software issue else you can even try
with other system since some application support Java and if Java is not
installed the prompt msg may not appear.
This would tell you why the msg didnt prompt.
Bye and take care.