One of two issues here…
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A faulty riser. Look at the 1X PCI side and make sure all solder points on the back side of the board are solid looking. Most of the time these are corroded and touching in some instances. Poor QC with most brands found on eBay and Amazon. Try known working ones to verify the card is not at fault.
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The gaming 5, at least in my 4 rigs, needs some modification in the bios to allow for up to 7 cards. Due to PCIe lane bandwidth I typically change my PCIe speed settings to Gen1 in bios along with 8x4x4 and 96 latency. Also change graphics mode to from IGP to PEG. But, you will have to plug your monitor into one of the graphics cards. You can also disable on board audio if you want. Try this along with making sure all risers are intact.
On a side note, keep trying different configurations and risers. Sometimes mobos can be finicky and need several reboots to recognize GPUs properly (at least with the way we build out these rigs). With that mobo as well you can check to see if the GPU is being detected via the hardware monitor in the bios. If you dont see it there, windows will not see it either. Once you see it here, if you are having driver issues (error 43, etc) than you can start messing with them.