Please see the below knowledgebase article on the Azure support site providing further information on how Azure SSO works with Huddle:

https://docs.microsoft.com/en-us/azure/active-directory/active-directory-saas-huddle-tutorial

Troubleshooting

If you receive the an 'AADSTS65005 invalid resource' error when testing connection (which may also expand on to suggest needing permissions for AAD Graph, as one possible reason reason here), you may need to add the additional information to the Azure configuration:

(Full message is like: AADSTS650056: Misconfigured application. This could be due to one of the following: the client has not listed any permissions for 'AAD Graph' in the requested permissions in the client's application registration. Or, the admin has not consented in the tenant. Or, check the application identifier in the request to ensure it matches the configured client application identifier. Or, check the certificate in the request to ensure it's valid. Please contact your admin to fix the configuration or consent on behalf of the tenant. Client app ID)