Lost screen on Panasonic 55 inch with Mac mini I tried to set the screen from the Panasonic to best fit.
When I did that on my Mac mini the screen went to snow.
I tried to get it back by on losing the HDMI cable power of the Mac. Nothing helps. When I start up the Mac the screen is going to snow. It works well on 720p and 1080i but can't go back there.
Try resetting your NVRAM (formerly PRAM).

Resetting NVRAM


Shut down your Mac. 
Locate the following keys on the keyboard: Command (⌘), Option, P,
and R. 
Turn on your Mac. 
Press and hold the Command-Option-P-R keys immediately after you
hear the startup sound. Hold these keys until the computer restarts
and you hear the startup sound for a second time.
Release the keys.


After resetting NVRAM, you may need to reconfigure settings for speaker volume, screen resolution, startup disk selection, and time zone information.