Hi ere,
HDMI micro may have been zapped by static from connecting or disconnecting HDMI plug while the equipment was on. I for one will raise my hand as guilty of this. A Factory Reset may help your case.
Simultaneously press and hold INFO and MUTE to enter the Service Mode. When the menu is displayed,
press 9 to start the factory reset. Don't know if it will restore HDMI, but at least you've tried.
Bruce