This post says the mute issue has been solved.
iqaudio-digiamp-muted-switch-t5012.html?hilit=Iqaudio%20mute#p23369
Is there a menu setting to Unmute on reboots? Sent an email request to IQAudIO a week ago but no reply. 
I have an IQAudio DigiAMP+, which is working without problem. I haven’t altered any settings anywhere other than to select the DigiAMP+ from the UI
Hello,
Check out Chapter 15 on page 34 in their user guide [IQaudIO User Guide v20].
Can be downloaded here: iqaudio.com/downloads/IQaudIO.pdf
Best regards, C
No joy. Only IQAudio DAC shows under Output Device.
So must you run a script executable on startup to remove mute? No menu pick? Please confirm?
In order to unmute the IQAudio DigiAMP+ HAT the following must be done to unmute on power off reboot.
For automatic unmute on boot, add the following lines to /etc/rc.local (before the exit(0))
#Unmute the Pi-AMP+
echo “22” > /sys/class/gpio/export
echo “out” >/sys/class/gpio/gpio22/direction
echo “1” >/sys/class/gpio/gpio22/value
Putting the line:
dtoverlay=iqaudio-dacplus,unmute_amp
in the file /boot/config.txt does not work.