I know this thread is a bit stale now. Just wonding if you've had any luck fixing this? We've also had this issue with the 2 of the 8 OptiPlex 7090 MFF we ordered last year. One of the 7090's was connected to a slightly older Dell Monitor and an older BenQ monitor. We've only had one occurrence of the issue on this machine. The one we've had 2 or 3 occurrences with is using monitors that we purchased at the same time. We've tried different DP cables. Usually we have to resort to turning everything off unplugging everything from the 7090 including power. Plugging the monitors back in and turning them on and then powering the 7090 on. Have just installed the 1.7.0 BIOS Update from May which hopefully fixes this issue. Originally thought it was the same issue as the link below but have not confirmed this. [URL]
We have a shipment of this model device.  We've noticed so far on about 10 of them, that the cpu works fine on newer monitors, but not with older monitors.  We've swapped DP cables, we've tried different power cords, upgraded bios, It has the Intel UHD Grahics 630 display adapter.  The 7090 has 2 DP ports, no other type to plug in to test.    Has anyone else seen or heard of such an issue? FranPLV
OPTIPLEX 7090 MFF - WORKS WITH SOME MONITORS AND NOT OTHERS