Hi JWilly,
Okay, you're actually dealing with a couple of issues here that get rolled into one.
Apple has paired the earpiece speaker assembly (which includes the speaker, flood illuminator and ambient light sensor) to the logic board. What that means is that only Apple can replace that complete assembly, as they are the only ones who can do that pairing.
So in short if the sensors on the earpiece speaker assembly are damaged, there's no way to recover Face ID without taking it to Apple for repair.
That being said, there are certain repairs that can be done to that assembly. Most of them, unfortunately, require extremely specialized skills and equipment that is beyond the capability of most home repair people like you and me.
HOWEVER, it is possible to replace just the earpiece speaker by itself if you can do a very minimal amount of soldering. I've written a guide for the iPhone X that shows how to do it, while the exact steps to get to the speaker are slightly different on the 11 Pro Max, the principle is the same. Here's how.
Follow the Earpiece Speaker Assembly guide up through Step 22 and stop there.
[guide|128662|iPhone 11 Pro Max Earpiece Speaker and Front Sensor Assembly Replacement - iFixit Repair Guide|new_window=true]
Pull up the iPhone X Earpiece guide and skip to Step 25. The parts will be laid out a little different and there may be tape at different locations, but those should be easy enough to figure out with a little common sense.
[guide|151215|iPhone X Earpiece Speaker Replacement Without Losing Face ID - iFixit Repair Guide|new_window=true]
That will get your earpiece working again without risking making your Face ID situation worse. I'll have to leave it up to other experts here on what you may be able to do to get the flood illuminator and/or proximity sensor working again.