MacBook spacebar and other keys not working for some time after startup and sleep - MacBook Air M1 2020

My MacBook Air suddenly had a problem with keys not working when first starting up or after the computer had gone to sleep. This first began after I left the computer on, but closed, overnight.

I have found many people posting about the same issue and I have just found that the SMC reset solved the problem.

Curiously, the SMC reset instructions say this should not be necessary for my M1, 2020 machine, but the problem has only been solved following restart while holding down the control, option and right shift key, as shown here for the T2 chip: Reset the SMC of your Mac – Apple Support (AU). According to the article my computer has an Apple Silicon chip and this procedure shouldn't apply, but it worked.

The dead keys on my MacBook Air were the spacebar, function key, tab key and down arrow.

When I opened the Keyboard Viewer none of these four keys registered when pressed on the inbuilt keyboard.

When I attached an external keyboard by bluetooth these four keys worked and did register in the Keyboard Viewer.

That made me think it was hardware related, but about 5 to 10 minutes after startup or waking from sleep, my inbuilt keyboard would start working again. The fault did not occur again while using the computer, even for many hours, but would immediately recur if the computer went to sleep (i.e. I closed the screen).

So, the old SMC reset for T2 chips seems to have solved the problem, even though it should not apply to this model of computer. I've restarted the computer since first trying the reset procedures and the keyboard still works fully.

I thought this might be useful to share.

Let me know if it works for you, particularly if you have an M1 computer (with an Apple Silicon chip).