The earspeaker is on top of the screen and needs to be switched from one screen to the other.
It may be that it is not correctly plugged in or the cable the speaker is soldered to was damaged during the replacement.
Good news is if the part it damaged it should not be expensive for a replacement.
The bad news is on the part there is also a sensor called the proximity sensor which plays a role in the faceid circuit. If the proxi sensor is replaced, face ID wont work any more. It will only work with the original proxi.
The proxi can be transfered from one flex cable to anothet one, but requires micro soldering.
That being said, everything else should work just fine after replacing that flex cable.
I hope this helps, let me know if you have any other questions