Apache fails to start due to: Failed to configure encrypted (?) private key

Symptoms

Apache is not running and the following error is logged to the Apache error log (/etc/apache2/logs/error_log) when Apache fails to start:

[ssl:emerg] [pid 2229] AH02312: Fatal error initialising mod_ssl, exiting.
[ssl:emerg] [pid 2229] AH02564: Failed to configure encrypted (?) private key
domain.tld:443:1, check /etc/pki/tls/certs/hostname.domain.tld.crt
AH00016: Configuration Failed

Description 

This typically occurs when using the SSLCertificateFile directive with an invalid path in a custom Apache includes configuration file.

Example:

# cat /etc/apache2/conf.d/userdata/ssl/2_4/cpaneluser/domain.tld/includefile.conf
SSLCertificateFile /etc/pki/tls/certs/hostname.domain.tld.crt

Workaround

By default, Apache's configuration contains an SSLCertificateFile directive for each domain. You can confirm this by running the following command:

# grep 'SSLCertificateFile' /etc/apache2/conf/httpd.conf

To resolve the issue, remove the SSLCertificateFile directive from the custom Apache includes configuration file, or comment out the directive by adding a '#' to the front of the line the directive is on. Once complete, run the following scripts to load the change and to start Apache:

/scripts/rebuildhttpdconf
/scripts/restartsrv_httpd