Microsoft Wireless Keyboard 3000 v2.0 not working

I have a Microsoft Wireless Keyboard 3000 v2.0 that was bought paired with a Microsoft Wireless Mouse 5000. They're both Bluetooth and use the same receiver.

The keyboard no longer works. The receiver is fine, as the mouse still works. The keyboard is still detected by Windows when the receiver is plugged in. The batteries have been replaced. There are no on/off switches on the keyboard or mouse, and no re-sync button on them or the receiver. Results are the same when using the receiver in a different USB port, or on a different machine.

Anything else I might try to fix this, or should I hold a funeral for the keyboard?

in the row of f buttons there isn't one for bluetooth?
also in settings/bluetooth and other devices have you performed a scan?

Do you know how to open control panel? If so then go to it and open "device manager", then go to "keyboards" see if the Microsoft keyboard is listed, if so then click on it and select "property's", select "update drivers", wait till it's done, if it updates then close everything and restart the computer, if not then you may have to delete the driver for that keyboard and restart, the computer should reload the driver on start up.

If that does not work then it may be time for a new keyboard/mouse.

maybe try this, On Win8.1, probably similar for Win10. Go to Settings, Ease of Access, Keyboard ... change the 'Filter Keys' to 'off' This setting states it is to 'ignore or slow down brief or repeated keystrokes
Also did you try RE/Pairing the keyboard, there's supposed to be a Pairing button on the Bottom of the keyboard to press
for pairing etc. ? if it's a driver issue then in device manager it will be listed as UNKNOWN DEVICE and should have a
yellow (!) beside it meaning wrong driver, If for some reason you can't find a updated driver for it
download a copy of Driver Booster, this software will check your PC/Laptop for outdated drivers and install updated ones
for it.