Title basically says it all — Immediately after installing Sierra on my 2012 15" rMBP, the Tab and Caps Lock keys stopped working. I haven't moved the rMBP and it hasn't been hit or damaged in any way, so unless it's the coincidence of the century, it seems like Sierra is the culprit. If I activate Caps Lock via the Keyboard Viewer, the green light comes on the actual Caps Lock key, so it seems like the key is getting power, etc. Has anyone else seen this? Any ideas on a fix? Thanks.