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after upgrade to sierra, key 1-9 isn’t working. but when i use external keyboard, its working fine. please help me

Could be a couple of things. Did you spill anything on it? Boot into Safe Mode by holding down the shift key on boot up. If it now works, get a Paid anti-virus such as WebRoot or Symantec Endpoint Protection and get rid of your virus.

More than likely, its a hardware issue. I had the same problem and replaced my upper case (easier and recommended over replacing the keyboard). For $50 and about 2 hours of methodical removal an reinstallation, problem resolved. I’m pretty mechanically inclined, but frankly if you can unscrew parts and put them back in with some patience, anybody can do this and save hundreds of dollars in labor. Here is a link to the part you’ll need, but shop around for pricing: https://www.macpartservices.com/661-5871… I used the IFIXIT video step by step: MacBook Pro 13" Unibody Early 2011 Upper Case Replacement Also make sure you have the following screwdrivers or bits before starting… It’ll make your life so much easier when changing out the case: https://www.homedepot.com/p/Husky-8-in-1… Phillips #00 Screwdriver Tri-point Y0 Screwdriver Good luck!