The problem reappeared, I am pretty sure that there's a problem on El Capitan as my keyboard

works on my MBP.

Keyboard is also not working even running on Safe Mode.

I deleted the file on /Library/Preferences/com.apple.keyboardtype.plist but it did nothing.

I did a SMC reset to fixed the problem as it did not work using OS X recovery.

Hello, like everyone else I had the same issue,  . After saying this, this was the second time it happened in two months. And apples send me a new one because I was under warrantee. It was Friday evening and I knew I couldn't call Apple until Monday. I went through all the procedures and exactly the same problem as everyone else was happening. After two hours I started to tap every key, two or three times, I had at this time on my desktop, the keyboard viewer, which was activated from the menu bar. Suddenly I saw certain keys started to be active on the viewer. I couldn't say which key triggered it, but obviously one of the  keys had been sticking. I have had an iMac it seems for 100 years, I also remembered in the distant past that this had happened a few times before. I suggest that anyone who is having this problem now should tap firmly all of the keys on the keyboard hoping it will release itself.

My iMac 2011 wireless keyboard shows the same problem in years! And Apple has done nothing since Mavericks to fix this ****. :(

Fixed my issue of no letters or number keys working - v fricking annoying!

Hope this helps.....Check this page OS X Yosemite: If keys on your keyboard don’t work

[BTW - am using El Capitane too]

My specific solve was:

Choose Apple menu > System Preferences, click Accessibility, then click Mouse & Trackpad. Make sure Mouse Keys is off. If Mouse Keys is on, pressing keys in the numeric keypad moves the pointer instead of entering numbers.

i have the same problem and nothing is working and I mean nothing! I am using another keyboard for now which is seems mines just went out with full batteries.

I had one of the logitech solar they are very nice and work great will run for like a month between chrges and it charges with regular light buld sweet keyboard i only changed when i upgraded my Mac. Ok as far as your key problems it very well could be the keyboard but before you go buy one go into settings the accesabilty tab look for the mouse settings now some of the mouse settings are in the moniter display settings IDK why apple thing what you are looking for is mouse keys if that box is checked uncheck it and try your keys same thing happened to me with the solar logitech keyboard and that was the issue took forever to figure out. I included a pic as you can see box un-checked

see my comment and pic below hope it helps

same problem here. left keys

123qwaszx not working

right keys opklnm90 not working

Did you ever figure this out? Mine is doing that now.

did you check this sounds like mouse keys are enabled

I'm running latest iOS on a mac. where to find this settings? Screenshot?

Found it, but I have to connect the keyboard first by typing a code. typing this code is as you understand not possible because the enter button is also not working.

Hey there I like this question made me think thanx so it sounds like you are trying too connect a new bluetooth keyboard to your mac is this true?? If not and you just have some keys not working you can use the tab button to highlight buttons on the screen aka then hit the spacebar too press said button. Or use the mouse if possible this may be a case of need more info thanx