I had a caesarian section in December 2014 due to prolonged labour of 19 hours after which my cervix ended up not opening. My question is, what might cause it?

Sometimes labor does not progress normally due to several reasons. These may include:
<ul>
<li>If you were induced, you may have had what is known as induction failure.</li>
<li>Were you able to move around during labour?</li>
<li>Sometimes failure to progress is due to unexplained reasons.</li>
</ul>