Currently, D365FO on-premise-LDB doesn’t support to show an error message as multiple languages when User is failed to sign-in D365FO because preferred language settings in User-option is not available before completing the signing-in D365FO in this scenario. D365FO on-premise-LDB should check the language settings of Web browser through the header value of http request in this case and show an error message with appropriate language that is matched to the language setting of User’s browser. (e.g. English UI should be shown if the language settings of user’s web browser) We would like to get this feature into D365FO on-premise-LDB in the future.