"This certificate was signed by an untrusted issuer"

Server
1

After installing the certs following “Let’s Encrypt Closed Beta Invite”, I got:

Error code: sec_error_unknown_issuer

from FireFox 40.0.3, Chrome 45.0.2454.93 and Safari 9.0.1

Here is the screen from Safari:

How can I check what’s wrong?

2

I wrongly included the nginx files, here are the corrected files for apache:

SSLCertificateFile "/etc/letsencrypt/live/exampl.es/cert.pem"
SSLCertificateKeyFile "/etc/letsencrypt/live/exampl.es/privkey.pem"
SSLCertificateChainFile "/etc/letsencrypt/live/exampl.es/chain.pem"