Does your SSLLABS report say ‘This server’s certificate chain is incomplete. Grade capped to B’?

Simple fix:

Concatenate the certificate file with the Intermediate CA.

Open your Certificate file and Intermediate CA in a text editor, copy all of the Intermediate CA file and paste it after the end certificate section.

JOVtnRpn3coVfSR/0rz0XKVXeZGnKztGdIMQhWMTxvZ1UpmRAH2Ab2QnVo1fkPVy
qNSJces5Y/VKpIvLBk5Jj55fvK8ME/9ASa+LtLrIms8iYHl75cupuYZZlg8=
-----END CERTIFICATE----- 

Leaving just the Certificate and the Intermediate Certificate in the file.

Restart your web server and retest in SSLLABS.