Это старая версия документа!

ginx[30854]: nginx: [emerg]
SSL_CTX_use_certificate_chain_file("/etc/nginx/demo.crt") failed (SSL: error:0200100D:system     library:fopen:Permission denied...e:system lib)
nginx[30854]: nginx: configuration file /etc/nginx/nginx.conf test failed

You probably have SELinux in enforcing mode (the default for Fedora):

sestatus -v

If this is the case, check the audit logs, you should find the access error:

ausearch -m avc -ts today | audit2allow

You also probably moved the filed instead of copying it, so the security context of the file might be wrong.

ls -lrtZ /etc/nginx/demo.*

and correct it if needed:

restorecon -v -R /etc/nginx