Symphony MK II Pro Tools HD cannot playback core audio outside of Pro Tools and shows 00.00 on the screen

When Symphony is connected to your AVID HD card check if Symphony locks to clock in Pro Tools and audio playback in Pro Tools is working normally.   If so this would be correct.

If Symphony does not lock to clock for playback outside of Pro Tools this is an AVID issue where you need to use the Avid Audio Server app to set the sample rate for core audio playback.

This is located in Applications > Avid > AvidAudioServer.

Please see the following document that explains AvidAudioServer and how it can be used with Symphony I/O MkII: Avid Audio Server + Symphony IO MkII