Here's what finally worked for me to reattach my 2016 Macbook space bar after removing it to clean: https://www.youtube.com/watch?v=qCrF9Cdn.... You basically cut the white lever in half lengthwise and then reattach just half of it to the key and keyboard. (The half that has the non-symmetrical holes attaches to the single pins side of the key.)
My space bar was sticky but not stuck, and I tried to reattach it for over 3 hours using josephpgrendon's directions, but could never get the lever to stick to the keyboard, even though all the little pegs were intact. I thought it clicked into place several times and put the black key on top, but that just made the black key and the white lever connect; the assembly wouldn't attach to the keyboard.
I didn't really want to cut the intact lever but I definitely didn't have time for the ~3 hour visit to the Apple store, so I did it. Now it works better than it did before I cleaned the key, but not at 100% - the space bar still occasionally misses when I don't hit it square.