Chosen Solution
After replacing battery and booting my laptop, my login screen comes up, but most of my keyboard became unresonsive. There are some keys working, but not all. Trackpad works, keyboard backlight works, but the rest of the keyboard is unresponsive. Please help!
See step #69 of this guide and reseat it: MacBook Pro 13" Retina Display Late 2013 Upper Case Replacement
