If you have recently applied CURL update and upgraded it to cURL 7.67.0 version, you may receive the following error in WHMCS while access Enom or other registrar domains:
CURL Error: 56 - OpenSSL SSL_read: Success
This is not related to WHMCS or Enom / other registrar issue. This is due to CURL issue. On cPanel server, you can downgrade CURL version to previous version using the following command:
yum downgrade ea-libcurl ea-libcurl-devel
Thanks! This helped me to resolve CURL Error: 56 error message on my server. Thank you!