I am trying to help our BI team and developer out. We can't seem to get a successful connection between Marketo and Informatica using the REST API. We get the following error below and believe it may be because of the grant_type.
You have the correct grant_type, so I don't know what you mean by "because of the grant_type." As Informatica themselves agree, "Marketo supports only the client_credentials grant type."
Is the REST URL supposed to include the /rest pathname? The Informatica guide indicates it's only the hostname.