Haroxy client certificat pb

I am using client certificat with haproxy (configred with ca file and crl-file )

I am seeing this error in the firefox:

SSL peer had some unspecified issue with the certificate it received

I am seeing this error in the haproxy:

SSl client CA chain canot be verified

I did not have any chain, i have only root ca and client crt.

I used $ openssl verify -CAfile ca.pem client.pem

to verify root CA with client certificat and the result is ok.

I used ca-ignore-err all in haproxy config and the pb is gone

Why ca-ignore-err all in haproxy solved the pb ?
what can i do in the log format to understand this pb ?