Using RC Viewer of version 14.0 and trying Remote control of 12.9 or lower RC Host machine's, then the clipboard actions are disabled .
<Please see attached file for image>
ITCM 12.9 or 14.0 Remote control Viewer. ITCM 12.8 or lower Version Host.
Please open a support ticket and request T5SM105.
Note : The above fix is for ITCM 14.0 . Please mention your RC Viewer version while opening a issue.