Ran into a similar issue last week.. the screen was dark(unreadable)... in the morning.
All the settings in MENU were Auto. I hadn't changed anything the night before.
After a few minutes of trying... I changed the HEADLIGHT KNOB to 'AUTO'. I had switched that off.. and this screen switched to the 'Day' mode.. and was the usual brightness.
I was surprised.. what all was driven by the 'Auto' setting of the headlight knob.
hope urs was something simple like that.
mine's a 2001 RX300.