This problem actually happened to me before. After a firmware reflash, my keyboard backlight also
stopped working and the media keys were not functioning.
I was really afraid I had to send in my keyboard until I was able to stumble upon this fix.
I notice that whenever I plugged in my keyboard, windows would reinstall keyboard drivers and whenever it was finished,
I would see on the bottom right corner of my screen "USB input device installed."
The corsair firmware utility would never recognize my keyboard whenever my keyboard was installed as only an
"input device" and I would get an error message "cannot open usb device, please reinstall driver."
After replugging in my keyboard like around 20 times, my keyboard was finally recognized and installed by windows as a "corsair keyboard."
Miraculously, the firmware update was also able to work its magic on my keyboard and I was able to regain my backlight and media keys.
I hope this post helps out other people with similar problems on this forum.
I don't know if this keyboard has problems that has to be fixed through its hardware or whether the firmware update was simply buggy,
but this problem can be fixed without a RMA if you guys just take the time to test out all your ports.
p.s. my computer has like 15 usb slots so I just plugged the keyboard into each port until it was finally recognized.