Thank you for your message.
Am I right in assuming that you use the 184.108.40.206 version of Remote Utilities? If this is the case, then could you please try updating your installation to the most recent 6.12 Beta 2
version and see if the blank screen option works for the external monitor this way and if you're able to see the custom text? In the 6.12 Beta 2 version, we have implemented a new blank remote screen mechanism that completely replaced the old driver-based mechanism and which allows adding a custom text to the remote screen when it is blanked. For more information on the release notes please see this page
When updating Remote Utilities, please make sure to update both Viewer and Host/Agent (as well as the RU Server if used) as the version mismatch might lead to performance issues and some features not working. The 6.12 Beta 2 version is available for the download on this page
Please let us know if the issue persists even after updating to the 6.12 Beta 2 version.