iPhone 6 ear speaker not working after screen replacement

Hi everyone!

My cousin cracked his screen on his iPhone 6 so I volunteered to fix it. The replacement went smooth in every aspect minus the ear speaker not working during phone calls, etc.

I've opened the phone back up and re-positioned the cables WITH the 4 prongs touching the 4 connectors on the ear piece half a dozen times. The ear speaker still doesn't work. I don't see how I could have broken anything, especially since the rest of the components work.

What can I do? I don't see what could possibly be wrong.