I just did this replacement today and had the same problem as the other posts. However what I figured out was that the speaker is powered through contact on the back side. I applied some pressure to that area (this is mostly likely bad for the screen, so try at your own risk) to the speaker area and surprise it worked. A hacky fix was to put a piece of folded up paper on top of the speaker to create the contact. I do not recommend this fix, but it help solidify the actual cause.
Hope this helps