The naming of the service could affect this, or the service may fail to connect. I’ve seen mis-configured Oracle services prevent anything from being displayed on the Services tab. An admin call to the API to delete the service should get everything working again, and then a check of the DreamFactory log may tell you what the error in Oracle connection was. If it is simply a matter of the Oracle call timing out (default Oracle admins have access to 10k+ extraneous system tables that can kill the PHP in DreamFactory’s stack if you try to return them all with a blanket getResources() call), then try just getTables() with ?names_only=true or try recreating the service with user credentials that have limited access to only a few tables.