Leave the battery out for a while. Also, back up your CCF then choose skip when upgrading the firmware.

Silly question, but did you check the contast wheel?
I almost sent one back to Marantz for this once and was the contrast. Happens to the best of us. I hope I'm not the only one.
:)

Does the battery charge?

Do you get feedback beeps or button action when you press the panel where the buttons should be?

Do the physical buttons function?

Hope this helps.