Enable debug mode and maximum error reporting in Joomla global configuration then retry to see if any errors output. Please note you can not use forgot login for super users as that's a security feature. Be sure to be testing with a regular registered user. They should receive an email with a new password to login after successfully resetting.

Joomla does not fail if SMTP fails; it simply falls back to phpmailer. Please change Joomla to phpmailer and see if CB can send emails. If it can your SMTP settings are likely incorrect is my best guess.

Then it's probably an SMTP certificate issue, which Joomla ignores. You should have an error message though if both debug mode and maximum error reporting are configured. The mailer has to be failing in some way, which would throw an error. If it's not throwing an error it's either never reaching the process of sending an email to begin with or your mail server is never sending the outbound emails. Check within CB > Configuration > Registration that the From Address is either blank (causes it to use Joomla configured from address) or valid for your domain.