Bonus not paid by employer - What actions I can take on this?

Hello, I was working with one Pvt Ltd company for 1.5yrs. This company is into staffing, deals with manufacturing companies. The company has not yet paid me a bonus amount. I was working for a period of 7th March 2016 to 9th June 2017. I continuously send them emails but not getting any revert on mails.
What actions I can take on this?

Dear Tejas,
A couple of questions needs to be answered here:
1. How old is your employer? I mean for how long have they been in business.
2. Does your monthly gross earnings fall under the eligible limits for Statutory bonus?
Regards
Rahul

1. How old is your employer? I mean for how long have they been in business. 5+ yrs
2. Does your monthly gross earnings fall under the eligible limits for Statutory bonus? Yes I got bonus for March 2016 Month in respective Diwali(2016)