SAML Response is missing a required email attribute - Slack SAML

Trying to use Auth0 as an Identity Provider to Slack.

I got the login functionality working by going into Applications → My App → Addons → Enabling SAML2 Web App → Setting up the Issuer, Identity Provider and Login URL in Slack. I’ve also set the Application Callback URL there in the “Settings” tab.

The problem is when I test the login in Slack I get the following error: " SSO hasn’t been enabled.
The SAML Response is missing a required email attribute. Please check your Auth0 settings."

Has anyone dealt with a similar issue before?