Bolis,
Before making any further changes, consider starting the system and running HWMonitor or similar on top, monitoring the GPU temperature so as to eliminate the possibility that there is a thermal shutdown, and initiate a medium GPU-intensive program- not the program that so quickly halts the system. Monitor the CPU temperature secondarily. If the RTX 2080 is a multiple fan design- which puts the GPU-generated heat into the case- that might trigger a system thermal protection. It's not highly likely, but anyway, with a new, higher power GPU, an idea of the system operational temperatures is worthwhile.
BambiBoomZ
PS: I've found Passmark Performance Test quite useful in researching and evaluating upgrades and changes. There's a free 30-day trial.
HP z620_2 (2017) (R7) > Xeon E5-1680 v2 (8-core@ 4.3GHz) / z420 Liquid Cooling / 64GB DDR3-1866 ECC Reg / Quadro P2000 5GB _ GTX 1070 Ti 8GB / HP Z Turbo Drive M.2 256GB AHCI + Samsung 970 EVO M.2 NVMe 500GB + HGST 7K6000 4TB / Focusrite Scarlett 2i4 sound interface + 2X Mackie MR824 / 825W PSU /> HP OEM Windows 7 Prof.’l 64-bit > 2X Dell Ultrasharp U2715H (2560 X 1440)
[ Passmark Rating = 6280 / CPU rating = 17178 / 2D = 819 / 3D= 12629 / Mem = 3002 / Disk = 13751 / Single Thread Mark = 2368 [10.23.18]
HP z420_3: (2015) (R11) Xeon E5-1650 v2 (6C@ 4.3GHz) / z420 Liquid cooling / 32GB (HP/Samsung 4X 8GB DDR3-1866 ECC registered) / NVIDIA GeForce GTX 1060 6GB/ Samsung 860 EVO 500GB + HGST 4TB / ASUS Essence STX / Logitech z2300 2.1 / 600W PSU > Windows 7 Professional 64-bit (HP OEM ) > Samsung 40" 4K
[Passmark System Rating: = 5644 / CPU = 15293 / 2D = 847 / 3D = 10953 / Mem = 2997 Disk = 4858 /Single Thread Mark = 2384 [6.27.19]