3132939 - Error during logon (REST_AUTHORIZATION_ISSUE) when trying to connect to SAC from Analysis Office

Error below occurs when trying to connect to SAC from Analysis Office:

---------------------------
Error during logon (REST_AUTHORIZATION_ISSUE)
Could not read the JSON metadata for OAuth from URL 'https://<SAC_TENANT>/oauth'. Probably the Versions public API is not available or 'JAVA Service' or 'Default' is configured for the connection on a XS-Engine based server. (REST_AUTHORIZATION_ISSUE)
---------------------------

The trace of AO (refer to SAP note 2129389), shows the following entries:
---------------------------
ERROR |AoPlugin |BrowserBasedLogonDialogSac.ExecuteOAuthWorkflow |ExeThread | Caught AutomaticHttpLogonException (aggregated) while executing tasks: com.sap.ip.bi.pioneer.core.Connections.Http.CrAutomaticHttpLogonException: Could not read the JSON metadata for OAuth from URL 'https://<SAC_TENANT>/oauth'. Probably the Versions public API is not available or 'JAVA Service' or 'Default' is configured for the connection on a XS-Engine based server. (REST_AUTHORIZATION_ISSUE) ---> Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
---------------------------

The logon works fine to access SAC in browser and SAC mobile.

Analysis for Microsoft Office

1. Try to connect to SAC system from Analysis for Office;
2. Confirm the error;

The URL 'https://<SAC_TENANT>/oauth' is not available publicly without credentials.

The /oauth endpoint must not require an authentication. Analysis Office (or any other client using OAuth2 workflow) should have open access to the URL.

Make sure that '/oauth' endpoint is publicly available without any credentials. Contact SAC administrators for guidance.

The test can be done in a tool like Postman, by simply calling (GET) 'https://<SAC_TENANT>/oauth'. When successful, it should display a JSON string as shown in the example below:

oauth, sso, authentication, logon, error, login, credentials, auth , KBA , BI-RA-AO-CON , Please use component BI-RA-AO-XLA , BI-RA-AO-XLA , Excel Addin , Problem