The Citrix Desktop Viewer is not supported in the Citrix XenApp environment. Full details on this can be found in this blog "Enabling Desktop Viewer for XenApp":

This states:
"Please note that the following is not a supported configuration. At this time, Desktop Viewer is only officially supported and tested with XenDesktop. However, if you would like to use Desktop Viewer in your XenApp environments, please continue reading."

Citrix does not support this configuration and neither does SilkPerformer.

If this setup has been configured the user will need to either disable that setting, or use the Citrix client (but not the desktop viewer) directly to record Citrix. Please refer to the SilkPerformer release notes for a list of the tested Citrix versions