Hi, I had this issue once, it turned out to be a server side problem. My server guy fixed it, this is what he said:
"ok.... ssl issue is resolved. i had to put the full chain cert in the ssl.conf file
just fyi, and in case it comes up again for any of your other customers, you create a fullchain,pem file and paste in the root certificate and the intermediate certificate from the cert authority and then enable that file in the ssl.conf file
SSLCertificateChainFile /root/.ssh/fullchain.pem
then restart the httpd service"