To reset and re-pair a wirless keyboard which won't connect...
Switch off the keyboard by holding down the power button for 3 seconds. Click the Bluetooth icon in the menu bar. If this isn't visible, go to System Preferences, Bluetooth, and turn it on. Click on "Set Up Bluetooth Device" or "Open Bluetooth Preferences". Turn on the keyboard by holding down the power button, but do not release it yet. Setup Assistant should find the keyboard, so click the name of the keyboard. Click the "Continue" button. Make sure you are still holding down the power button. You will be prompted for the Pairing Code. You can now release the power button. Type the pairing code on the keyboard and press return. Pairing should happen now. It will take a second. The keyboard will now be paired, and should work correctly.
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