Have you changed the name of the PC recently?
If not go to the 'Services' in Windows and check to see if the 'Agilent Instrument Service' is started. If not start it.
If that fails you may need to reregister the system as an instrument controller, assuming this is a workstation installation?
To reregister the system as an instrument controller, you can click the Windows icon and search for 'OpenLab Configuration'. If you are running a workstation then you should just be able to click connect then apply. If running a Workstation Plus, then you need to click connect and enter an OpenLab admin username and password, then click apply.
You MUST restart the PC, in fact if you click OK at the end of the re-register it will automatically reboot the PC, so be warned!