Found this information on the link http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=1007&top=29
What do you mean by Primary Occupation?
Your primary occupation means the job you have experience in (within the last five years) and want to base your immigration application on, if you are invited to apply.
My NOC since last 4 years is 4031 (Secondary teacher)
and before that for 7 years experience is 4011 (lecturer)
In my primary NOC i mentioned 4011. Can that be the reason for ineligible status?