Z590 UD AC, Intel i5-11600, 16GB(2x8) Corsair Vengeance DDR4, no GPU, Asus PB258 monitor, DP cable.
At power up, if the monitor has just been powered up the mb boots normally, including POST display, and loads W11.
If the monitor is in standby mode the mb beeps 5 times and the VGA light stays on. No POST display but W11 loads.
I think 5 beeps from Aptio V means no console input or output which would be consistent with the monitor being off.
It has done this intermittently for over a year - 9 times out of 10 it would boot normally even if the monitor was in standby.
But now it will not boot normally unless the monitor has just been powered on.
Any ideas as to why the mb would usually detect the monitor in standby mode but not do so occasionally.
And why has this intermittent behaviour now become regular? There have been no hardware changes. I've replaced the DP cable with a new one to no effect.
