User's may see the following error message when launching applications or Desktops "Unable to Start, You might be having an issue with a Citrix virtual driver (****). Contact your system administrator for further assistance",

where **** is the name of a 3rd Party application or driver (eg MyBadApp). 

The issue may have started after uninstalling or upgrading a scanner driver or another 3rd party application.
 

1. Open the registry as a user with administrative access
2. back up the registry.
3. Browse to HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ICA 3.0.
4. Open the entry: VirtualDriverEx and look for an entry that matches the name mentioned in the error message under (****) (eg MyBadApp)  
   • 
5. remove the entry and the preceding comma. Do not remove or modify any part of the other entries under VirtualDriverEx.
6. Click OK and try to connect to the application 

Problem Cause

• Some 3rd party applications for peripherals such as Scanners or some Communications applications can utilize a custom Virtual Channel to provide some additional functionality. 
• Stale registry entries for these custom Virtual Channels can be left in the registry if the 3rd party application is uninstalled or upgraded incorrectly.

Virtual channel allow list policy settings: https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/policies/reference/ica-policy-settings/virtual-channel-allow-list-policy-settings.html