Hi: This is a question...I wish it were an answer! I just got a new macbook pro 13" (2017) and I am also having this problem. Tried PRAM but could not access the keyboard or the mouse. Also tried holding down the caps key. Tried all the solutions above, I have an adapter for USB-USBC, so I plugged in an external Apple mouse, and now my cursor works but I still cannot access the keyboard, so I can cannot log in. I plugged in an external keyboard (not Apple), and that also did not work. So I'm stuck....any ideas?