Chosen Solution
Suddenly keys one til nine won’t work. I found a bunch of people with the same problem and it seems very common, yet nobody has ever found a straight answer for it. One thing that does work: pressing all the faulty keys at the same time. That seems to wake them up temporarily, which shows that hardware-wise, the keys are still connected and working. To be honest, ever since I upgraded to High Sierra, this computer has gone downhill. I fear the good times of Apple computers have reached a peak about three years ago.
Did you have a liquid spill at some point into the keyboard? Your symptoms points to that. Luckly, replacing the uppercase is so inexpensive on this series I would just do that. Here’s the needed part: MacBook Pro 13" Unibody (Early 2011-Mid 2012) Upper Case and heres the IFIXIT guide: MacBook Pro 13" Unibody Mid 2012 Upper Case Replacement. While replacing the keyboard alone is also possible this is by far the better path.
