Well review your question first... you just said the button won't lock because it seems to be stuck in the pushed position right? So what does that have to do with your sn95 brake swap. The button is the lock/unlock which you know of course but I feel better saying it. Check the button make sure it's not stuffed with goowy **** around the outer part of it. Make sure the spring still works
Try to pull the button OUT then try it. Now unless you meant you did your swap and you can't figuree out the cabling, that's something that should have been said but it's all good.