Am I right in assuming that your remote Host machined is headless, i.e. no physical monitor is attached to it? In addition, please clarify what version of Remote Utilities do you use?
In case if you use version 126.96.36.199 or an older version, please try updating to the most recent 6.12 Beta 2 version as the issue you've encountered might have already been resolved in the most recent release. The 6.12 Beta 2 version is available for the download on this page. When updating Remote Utilities please make sure to update both VIewer and Host/Agent to the same version as the version mismatch might lead to performance issues and some features not working.
In addition, please try enabling the Use legacy capture mode feature in the Host Settings -> Other tab. After enabling the checkbox please make sure to restart the Host.