The accepted answer is correct.

The response to the string descriptor request 0xEE is only the first step of three.
You must answer 2 more requests that will come from your Windows.

If you want to see how a correctly implemented MS OS descriptor response looks like, read this here:
https://netcult.ch/elmue/CANable%20Firmware%20Update/#Ms_OS_Descriptor

At the end of the page you find an open source code that shows you how to implement the 3 descriptor requests in firmware.