When purchasing SSL from the SSL providers in many cases you will not get the chain certificates and you need to find them on they site, to make things easier we will add some easier instructions here.
For start check your domain certificates
https://www.sslshopper.com/ssl-checker.html
or
https://www.sslshopper.com/ssl-checker.html?hostname=YOUR-DOMAIN
If you get a broken end (red arrow) this could mean you have incorrect chain certificate or you don't have it at all and you need to correct it.
You can get your chain certificates here
https://whatsmychaincert.com/?YOUR-DOMAIN
Download your certificate file and open that file with the text editor, then in CWP go to Left-Menu --> Apache Settings --> SSL Cert Manager and click on the BUNDLE button to edit chain certificate file, replace all you have in that file with the new content.
After you have saved BUNDLE file reload Apache and check your SSL again.
https://www.sslshopper.com/ssl-checker.html