Employer not granting gratuity. Please advise what can be done ?

Dear Sir, I had worked for my previous company from Jan-2007 to July-2016( 9 Years 7 months). But in that whole span i was not gone for office for one month(2012-April month) with unpaid salary but i did not resigned. But that employer is rejected my gratuity saying that the service is not continuous. Kindly advice me that am i really not eligible to get the gratuity for the 9 Years 6 months service. Thanks and regards