Potential problem with RAM slot
Try spraying the socket, back of the cpu, and said faulty ram channel with some 99% isopropyl which should clean any filth that may be causing the slot to malfunction.
HP Z840 Workstation 2x E5-2630 V3 Eight Core 2.4Ghz ...
Thông số kỹ thuật HP Z840 Workstation ; Expansion Slots, PCIe Gen3 x16, 1 PCIe Gen2 x4 slot/x16 connector, 1 PCIe Gen2 x1 slot/x4 connector, 1 PCIe Gen2 x1 slot, ...
Dell PowerEdge T320 Systems Owner's Manual | Dell Australia
Faulty Wifi card slot (needs reflow) and/or faulty resistor R134. Proven by pressing down on the WIFI board and trying to boot.
2-Slot PCIe Gen3 x16 - Expansion Backplane - BRESSNER
OSS2-Slot PCIe Gen3 x16 Expansion Backplane ✓ 1x PCIe x16 slot ✓ 1x PCIe x16 target slot ✓ OSS-PCIe-BP-2019 ➤ Request now!