XPS 8500, no display issue

Hi everyone, I’m trying to revive my old XPS 8500 (I7 3770 with 1660 Ti and 500watts PSU) and upgrade it with some better components. However, I'm currently stuck with a "no display" issue on the GPU. When I use the motherboard's HDMI port, the display works fine, but when I connect my monitor to the GPU (tried both HDMI and DVI ports), there's no signal. I haven’t tried the DisplayPort yet, though.

The GPU fan is spinning, and I’m using the 6+2 PCIe power connector from my PSU. I just want to ask if there could be any other possible reasons why my GPU isn’t displaying anything on my monitor?

BIOS: A14
Boot: UEFI
Secure Boot: Disabled