My 2 cents:
Keep the recipe simple (have you tried 100% pilsner malt?). Avoid late hops (read: first wort only). IMO correct water is a big factor here - Martin did a great write up on this a while back for Zymurgy I think. WLP029 is my go to. As Major mentioned, in can be temperature finicky. I've had sluggish starts at 62° while 64° takes off.
I love this style and brew a lot of it.
This simple approach took BOS at Beer & Sweat last year (humblebrag). Happy to share any and all info you want.
Edit: Zymurgy feature was May/June 2017. "Water for Kölsch Brewing" by Martin Brungard. Featured in "Kölsch" by Dave Clark.