The Citrix Receiver is not installed or has become corrupted.

Verify that Citrix is installed:
  1. In the Control Panel, select Add or Remove Programs  
  2. Scroll to find Citrix Receiver in the list of programs
  3. If Citrix Receiver is not listed Install the Citrix Receiver
If Citrix is already installed:
  1. Uninstall Citrix Receiver via Add or Remove Programs
  2. Download and Install the latest Citrix Receiver