When using OAuth 2.0 Client Credentials Grant as a Connected System Object's authentication, the following errors are seen in tomcat-stdOut.log even though the connection is successful:
ERROR com.appiancorp.connectedsystems.http.execution.AppianHttpRequestExecutor - ConnectorRuntimeException [title=Connection failed, Could not authenticate with the connected system or connect to the external system at the specified URL]ERROR com.appiancorp.connectedsystems.http.execution.AppianHttpRequestExecutorPipeline - Could not authenticate with the connected system (UUID: <UUID>) or connect to the external system at the specified URL (<endpoint>). Check that the credentials in the connected system are correct and test the connection.
There is also a log entry line about OAuth token retrieval:
INFO com.appiancorp.connectedsystems.http.oauth.HttpOAuthTokenRetriever - Error while retrieving token: request_error attempting to pass Authentication in body
The OAuth 2.0 endpoint is incorrectly configured to expect Client Credentials in the request body.
Appian follows the ITEF RFC 6749 standard for OAuth 2.0 Client Credentials Grant. This standard specifies that including the client credentials in the request body is not recommended.
Appian sends client credentials in the authentication request header (as this is the preferred way by ITEF RFC 6749). If the request with credentials in the header fails, Appian will try again with the credentials in the request body.
Configure the OAuth 2.0 endpoint to expect Client Credentials from Appian in the request header.
This article applies to all versions of Appian.
Last Reviewed: January 2026