unable to verify the first certificate

[nikkopegmail.com]

Has anyone faced this problem with haproxy and ssl certificate.

Everything works otherwise, but when checked with openssl, we get the following error:
verify error:num=21:unable to verify the first certificate

The openssl command:
openssl s_client -servername some.server -host 1.2.3.4 -port 443 < /dev/null | grep subject=CN

The certificate purchaced from ssls.com and the CA is added succesfully in pfsense.

br, Pete