For a certain delivery group a usb mass storage device is not using the generic but the otimized ica-channel.
 

1. Identify what type devices to redirect and identify the class ID of the devices.
2. Once you had the class ID of device, force the use of Generic USB over optimised by setting the "AutoRedirectStorage" value in the client registry

Problem Cause

Plain Storage Devices (Mass Storage Device)

For plain storage devices, the best user experience is achieved using the dedicated virtual channel (such as Client Drive Mapping (CDM)) that also performs optimization.
However, in addition to simple reading or writing files, to perform certain special tasks like burning a CD/DVD or access encrypted file systems devices, the device might still need to be redirected using Generic USB support.

The following registry is used to configure whether or not plain storage devices are automatically redirected:[HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\GenericUSB\Devices]
"AutoRedirectStorage"=dword:00000000 

The default is 0 (do not automatically redirect), but changing the value to non-zero causes plain USB storage devices to be redirected by Generic USB support.

Active Directory policies can also deploy this value to the following registry key, and override the non-policy value if both are present:
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Citrix\ICA Client\GenericUSB\Devices]
"AutoRedirectStorage"=dword:00000000
Note: Read only access to the plain storage device is not configurable if using Generic USB support, while same is configurable if using CDM.