On some versions of Linux (Redhat) the cacerts file is not getting updated with your SSL certificate on install of LUNA.
The cacerts file is located in ~LunaImaging/7.x/LUNA/jre/lib/security/cacerts
You will need to use keytool to add the cert
keytool -import -alias mycert -file <Path to your SSL cert file> -keystore <Path to your cacerts file >
keytool -import -alias mycert -file /etc/apache2/ssl/www_example_com.crt -keystore /home/luna/LunaImaging/7.x/LUNA/jre/lib/security/cacerts
You can find the keytool in the ~LunaImaging/7.x/LUNA/jre/bin directory if it's not in your PATH.
This process will need to be done after each upgrade of LUNA.