Hi,
I had same problem , after huge time of research and trying , here are the solution :
I was using godaddy ssl certificate , I had to merge both server.crt and intermediate-certificate.crt into one crt file bundle.crt ,
I used the following command :cat server.crt intermediate-certificate.crt >> bundle.crt
I used the following command in terminal and than edit the nginx configuration file and changed crt path to the new merged crt.
than restarted nginx : sudo /etc/init.d/nginx restart
And it worked 