MacBook Pro Input/Output audio not found I have an audio problem on my MackBook with the following specifications:


MB Pro Retina (13 inch Early 2015)
Operation System: macOS Sierra 10.12.5 


Here is the chronology of the problem: Initially, everything was okay. I could hear music from iTunes on my MBP connected with a cable to an external speaker. Then I accidentally unplugged the cable on the speaker, so I plugged it in again but then I couldn't hear sound from my MacBook anymore. 

I have tried the following solutions to address this:


Restarting my MacBook
Reinstalling my operating system
Resetting both NVRAM and SMC
Plugging and unplugging to/from the audio jack on the MBP
Killing coreaudiod on Activity Monitor
Deleting the apple.bezleservices.plist file at ~Library/Preferences/com.apple.BezelServices.plist
Taking it into Apple Store Service near my town


The Apple Store said it was a hardware issue, but I'm not sure on this. So, I went home to try the various "non-hardware" approaches above.

FYI: My iTunes and Siri also don't work. Playing a song in iTunes shows no song progress. If I try to use Siri I get a "no audio found" message.

Below are various screenshots of my problem:



My questions:


How can I troubleshoot this further? 
Is there a way for me to narrow down whether or not this is definitely a hardware issue?
I just experienced a similar problem.  I discovered that when I plugged in my external speakers (in the radio plug port), my System Preferences defaulted to a lower volume output setting (presumably to prevent blasting out too much volume in small speakers).  Try opening System Preferences and resetting the output volume to a higher setting.