I also get the message

SSLCertificateKeyFile: file '/path/to/file' does not exist or is empty

while /path/to/file exist and have right permissions, just because of SELinux turned on and this file was unaccessable for apache user.

It looks like this:

$ sudo ls -laZ /etc/pki/tls/certs/
drwxr-xr-x. root root system_u:object_r:cert_t:s0      .
drwxr-xr-x. root root system_u:object_r:cert_t:s0      ..
-rw-------. root root unconfined_u:object_r:cert_t:s0  this-one-works.crt
-rw-------. root root unconfined_u:object_r:admin_home_t:s0 this-one-is-unaccessable.crt

I also get the message

SSLCertificateKeyFile: file '/path/to/file' does not exist or is empty

while /path/to/file exist and have right permissions, just because of SELinux turned on and this file was unaccessable for apache user.

It looks like this:

$ sudo ls -laZ /etc/pki/tls/certs/
drwxr-xr-x. root root system_u:object_r:cert_t:s0      .
drwxr-xr-x. root root system_u:object_r:cert_t:s0      ..
-rw-------. root root unconfined_u:object_r:cert_t:s0  this-one-works.crt
-rw-------. root root unconfined_u:object_r:admin_home_t:s0 this-one-is-unaccessable.crt

To fix this, I run sudo restorecon -Rv /etc/pki/tls/certs/ - it will repair SELinux property for the problem file.