[SalesForce] Salesforce Marketing Cloud Single Sign On Error – SAML SSO Error

You can pass a session ID as an attribute in the SAML Assertion. In the Connected App configuration for your SP, set $Api.Session_ID as a Custom Attribute value. The recipient will be able to use the session ID with the REST API.

The Authentication Service section in My Domain shows up the SSO configurations only if SAML is enabled in your Org and that My Domain is deployed. Refer to the below excerpt from the documentation for Add Identity Providers to a Login Page (emphasis mine):

If you’ve enabled single sign-on and configured SAML, or set up external authentication providers as Auth. Providers in Setup, you can provide links to these identity providers on your My Domain subdomain’s login page

You must deploy My Domain before editing authentication configuration settings.

To enable SAML, you can find details on the documentation, screenshot below.

Once you enable the SAML, you should be able to view the SSO configuration on My Domain page under Authentication Service when you click on Edit button.