Points to either antenna or hardware issues. You didn't write about checking the antenna connection from the board to antenna. Time to check that out.
Also, if you use Microsoft supplied drivers, I'd go get the driver that the motherboard maker issued and install that next.
Last, if all fails to budge, try some USB WiFi stick.
I've been stumped on this for about a week now, so I'm hoping someone here can help/offer suggestions. I've found several threads on this topic, but none quite like mine and none where the suggested solutions worked for me.
I recently built a new desktop PC, Ryzen 5 1600 in a ASRock Fatality X370 Gaming Micro-ITX motherboard. The mobo comes with integrated wifi, the Intel Dual Band Wireless-AC 3168.
My home network config is TPLink Archer C7 Router with a Netgear EX3700 Range Extender. I have both the 2.4 and 5 ghz channels enabled.
I fired up the PC, installed Windows, and promptly connected to the 5 ghz channel, which was getting me a blazing 85mbps download speed per Speedtest. Everything was running like a dream.
Fast forward two weeks. One day I boot up the PC, and suddenly I've got no internet connection. I'm connected to the 5 ghz channel, but no Internet access. I ran all of Windows 10 auto-troubleshooting doodads, updated the driver for the onboard wifi, rebooted the computer repeatedly, reset the cable modem, router, and access point multiple times, and verified that both channels are enabled on both the router and the range extender, but to no effect. I can still see the 5 ghz network (called _5GEXT) and connect to it, but when I do, there's no internet access.
The computer connects to the main wireless network from the router just fine, it's just that the speed is slow from this far away (and no real way to move it closer). I can also connect to the 2.4 ghz channel from the range extender (called _2GEXT), though that also suffers on speed (I get 6-15 mbps download speeds on these channels).
Today, I was able to get a shoddy signal on the 5 ghz channel for about 3 minutes (2 mbps download speeds), and then it stopped working again at all.
The weird thing is that nothing, so far as I can tell, has changed. My phone still connects to the 5ghz channel fine as does my Dell laptop.
So, what do you think? Any ideas? Any help would be appreciated. I really liked those faster speeds!