Welcome to the ROG forum.
What monitor do you have? Does pressing the power button turn it on with the DP cable?
Have you updated the motherboard bios to the latest?
The monitor is AOC q2778qve, though I have not been able to update the drivers as the AOC site was down when I tried. Restarting the monitor did not help.
What did help was changing the bios from version 1.3 3/23/22 to version 1.9 11/10/22, which appears to have restored my display port video so far! I want to run some further tests, but thanks so much for
the excellent help!