I’m so very glad to have found this fix before I went and spent either $ on a new keyboard (and time to replace it), $500 on a used Macbook Air, or the almost $2,000 on a new Macbook Pro. My Macbook Air (2012) had been acting up the past couple weeks – the keys on the right-side of the keyboard started to not work. The <ENTER> key was probably my biggest problem, but the ‘o’ and ‘p’ and comma stopped working as well. I assumed this was a hardware issue because if I banged on the key really hard, it would work!
So before I went out and spent $$, I googled this some and people were talking about a possible loose keyboard wire, etc. Then I stumbled upon this information over on iFixit. Resetting the SMC is not something I thought of for this issue as it was, to me, so clearly a hardware problem.
I tried it anyway, just (while Macbook is powered on) hitting the CTRL-OPT-SHIFT-POWER then powering the machine back on. This worked immediately! So relieved to have one less thing to worry about buying this month.