Replaced loudspeaker & Lightning Connector - still NO SOUND! :(

My iPhone 6 was dropped, and the loudspeaker stopped working.

I have purchased and replaced the following parts:

- iPhone 6 Loudspeaker

- iPhone 6 Lightning Connector and Headphone Jack

There is still no sound from the loudspeaker. (No sound in speakerphone mode, no sound in videos, music, no alert sounds. Sound is only heard in phone calls if non-speakerphone mode is active. )

Everything else on the phone seems to work. Sound works in headphones.

I have also tried:

- Resetting the phone to factory state.

- Ensuring that the volume is all the way up.

- Ensuring that the headphone icon is not visible.

- Ensuring that Bluetooth and AirPlay are off.

- Ensuring that the lock button is off.

It seems like there must be some other hardware issue. There is a large crack on the bottom-right corner of the phone. is there any other part I can replace, or is there any way to further diagnose this issue?