Thanks, that helps. It looks like your SSO provider site is a WordPress site. Are you using the WP Discourse plugin for SSO? If so, and you are using the latest version of the plugin, try going to the user’s profile page and checking the ‘Email Address Verified’ checkbox. Then be sure to click the Save button. After doing this, have the user try logging in again.
If you are not using the WP Discourse plugin, we will need to give you more detailed instructions to fix the issue.