Outbound REST Message for sn_external users

Currently have some outbound REST messages configured with OAuth 2.0 Authentication type to MS Graph endpoints. I have created all of the methods and OAuth profile in global scope and currently seeing an issue while impersonating sn_external user. It looks like the OAuth call to login.microsoftonline.com is not triggering for them. The other calls are triggering but fail due to invalid token. Any ideas? Do i need to create an OAuth profile in CS scope for sn_external users?