iMac Suddenly HDMI Display and Mirroring Not Working

2009 iMac. Iuse display to HDMI converter for my TV. The audio suddenly stopped working on the TV andplayed through iMac only. About a week later the display suddenly stopped working altogether out of nowhere. I have tried different HDMI cords, HDMI converters, and different televisions with same problem.

The display isn't even showing in Preferences and the monitor icon isn't showing on the top menu bar anymore. When I unplug and plug HDMI back in it blinks like something is recognized but then shows "no signal". Also tried every combo of resetting TV, turning TV on then connecting HDMI cords, restarting iMac, shutting down iMac with HDMI plugged in and not... all same symptoms. Formatted drive and installed fresh Yosemite, still same problem so it is VERY frustrating!

Any ideas?