Are you sure you are passing an attribute called "username"?
IdP Attribute Information
Certain attributes are required by most IdPs. The following list outlines these attributes, and where to find that information in Dashboard:
- Entity ID
For Dashboard SSO, this is https://dashboard.meraki.com - Assertion Consumer Service (ACS) URL
This is provided as the Consumer URL on the Organization > Settings page under SAML Configuration. It will be unique for each organization. - Username attribute
A username attribute must be passed in the SAML token/assertion, specifically 'https://dashboard.meraki.com/saml/attributes/username'. This includes the name the user will be identified as in Dashboard. Mapping this to an e-mail address is strongly recommended.
Note: This attribute cannot match an existing Dashboard administrator or Meraki Authentication user's email address.
Note: Dashboard will only accept one role attribute. If multiple roles or group memberships are provided, the first attribute will be used.