iPhone 12 Pro Max - Headphones not working

I have headphones that used to work on my iPhone 12 Pro Max, but it suddenly stopped working. I can plug in the charger and it works fine, so the issue does not appear to be the port. This started happening months ago and it's still not working. I have rebooted several time since then and updated the software. I am currently at 16.3. I've checked for any settings that may be causing this, but I cannot figure out why this is happening. Does anyone have any ideas?