There is a two stage process with our devices when connected to USB.
When first plugged in they enumerate as a simple PicoScope device, they are not a fully function scope at this stage. When the software opens the scope, the driver will load the runtime code into the device. At this point the scope will perform a restart, and will then re enumerate on the USB bus again but as a different device. It is this dual operation that can cause these extenders some difficulty, and you need to identify the device in the extender software a second time.
If you open Device Manager, and then open the software, you can see this double operation in progress.
I don't have access to a Silex device, or it's software, so can't say exactly what settings you will need to change.