Solved from my end (Apple Wireless Keyboard A1314)
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I have a similar problem with my wireless keyboard A1314, keys 1-8 suddenly stopped working. I figured out a solution to this issue, I've taken out the grey cover at the bottom-center, try to press the keyboard flex that is connected to the pvc, I think it might have loosen in some way over time. After trying this, my keyboard fortunately was back to its working condition. Hope this works for you too.