I have had this same issue testing today. This is not a solutions, but I am including some more details and troubleshooting. Using a Microsoft Surface 7 running Windows 10 with standard Lenovo US keyboard. Once the computer locked and went to sleep, the keyboard was no longer responsive. It would not wake the computer as usual. I woke it with the mouse. I then tested typing with no response. I also checked the NumLock and Caps Lock LEDs. They functioned. I checked my streaming to C2. The keystrokes were still being picked up by the KeyCroc and being sent to C2. They just were not passing to the computer. When I unplugged the keyboard from the KeyCroc (leaving the KeyCroc plugged into the computer), it still would not work. My issue also required me to remove the KeyCroc from the computer to allow it to reboot before it would work again.
To further test, I tried to duplicate the issue. Once connected and functioning correctly, I tried removing the keyboard from the KeyCroc and reconnecting. It continued to function once reconnected. I also checked the Device Manager to see if there was a power saving option that was causing it to disconect or sleep in some way like a network adapter. This was not the case. I did find if the computer was locked, but did not yet have time to go to sleep, the keyboard would continue to function after unlocking. Manually causing the sleep would duplicate the issue. I did notice that the HID Keyboard Device (on USB input device) continued to remain in the Device Manager when the keyboard was not passing input to the computer.
I am not sure if it is relevent, intended, or a separate issue, but ever time the KeyCroc boots, the USB keyboard (showing as a HID Keyboard Device) resinstalls. It is quite noticeable because it connects, disconnects, and reconnects a time or two with an audible alert each time. This could be an issue in deployment.