Let's encrypt error

After I enabled the Let's encrypt (Under WAF) , I get this error:

Logging:

2018:09:24-12:14:12 mail letsencrypt[8563]: I Create account: creating new Let's Encrypt acccount
2018:09:24-12:14:12 mail letsencrypt[8563]: E Create account: TOS_UNAVAILABLE: Failed to retrieve current Terms of Service from remote server: 500 SSL_ca_path /etc/ssl/certs is not accessable
2018:09:24-12:14:12 mail letsencrypt[8563]: E Create account: failed to create account