No audio devices on Macbook Pro (Late 2011) I have a Macbook Pro (Late 2011) running macOS Sierra that cannot recognize any audio devices. No headphones, no speaker, no microphone. I currently use a USB audio card, which works fine but isn't convenient.

I have tried to fix this by:
Reinstalling the OS
Resetting PRAM
Blowing compressed air into audio jack (and cleaning the whole computer)
Repairing disk permissions
Removing ~Library/Preferences/com.apple.BezelServices.plist and rebooted

I also booted into my Windows partition which did not recognize any audio devices either. So, it sounds like it is hardware related. Any ideas on what can knock out all incoming and outgoing audio at once. I opened it up and didn't notice any disconnected cables or anything of the sort.
The sound chip or the connection is probably broken. Try Apple Hardware Test or Apple Diagnostics. Depending on the issue it might be able to detect the malfunction. If it detects nothing, it might be a clean break. If it gives you an error code, it could indicate the location of the failure.