Hi Everyone. At the end of my troubleshooting skill with this issue.

I just upgraded my network at home to a hybrid 1gb/10gbe system. Here's my setup and my issue (as well as my already failed troubleshooting).

I have a smart managed switch with 4 10gbe ports on SFP+ fiber using LC connectors. All my transceivers are the same model Intel 10Gbe SR. One of these is empty, the other 3 are populated like this:

Port 27 & 28 are aggregated at the switch and teamed at my media server (windows 7 with a x520-sr2 NIC, same transceivers, and its operating at the full 20gbps)

Port 26 is connected via 10gbe fiber to a qsw308s unmanaged 1gb/10gbe on one port, and then the other two ports go to two different windows 10 pc's in my office (one is AMD, other is an i9 9900) each with x520-sr1 NIC's (as well as onboard realtek or intel 1gbe connections).

So far, this works fine as the 1gbe ports on the office switch (qsw308s) are functioning 100%, all devices passing through with no issues (an arlo camera system, 2 printers, and 1gbe connections x3 to the PC's). The transceivers are on the compatible intel transceiver list from both switches.

The x520-sr1's are showing working with no conflicts in device manager, showing connected etc...but showing network cable unplugged. Now, this only occurs in Windows 10....when the systems are on, the lights are on for both the NIC and the switch at both ends, but it says network cable unplugged. Here's the weird part...during bootup and shutdown, the NICs on both PC's pull IP Addresses from the router, both IPv4 and IPv6, and they stay active when in the BIOS...as soon as windows loads, the connection is lost and the IP's are gone.

Turning SR-IOV on and off in the bios makes no difference, and I'm not running any VLANs yet.

Also, when troubleshooting during the "enable/disable" process during a cold boot they will pull IP's for a split second and then lose them again.

Needless to say, I'm convinced this is an issue with Windows 10.

Here's what I've done to troubleshoot;

Windows 10 troubleshooter is useless, it either says plug in the cord or cannot solve.

Uninstall intel networking software and any installed VPN software via control panel, empty all caches and temp files, disable and uninstall adapter, reboot, windows 10 reinstall with latest drivers, nothing.
As above with 1gbe port disconnected, manual install of drivers from intel (both version 20 and version 25) and nada.

Disable/Enable - network cable unplugged. When disabled, lights go out on both the switch and the Transceiver.

Disable/Shutdown/Unplug overnight/Plug in/Power On/Enable - gets an IP for a split second then loses it. Lights are out on the transceiver and switch when disabled.

Ipconfig /flushdns - network reset (windows 10 reboots etc) - nothing changes, IP when booting or in the BIOS, network cable disconnected when in windows).

Swapped known working transcievers from x520-sr2 server to either end of the x520-sr1's and the qsw308s. No change.

Swapped known working fiber cables from x520-sr2 server to either end of the x520-sr1's and the qsw308s. No change - both sets of transceivers tested.

Attempted changing settings - receive side scaling off, cannot set to 1gb / half duplex or the lights go out.

Ipconfig /release /renew does nothing also, it only impacts the 1gbe wired connection as the fiber shows no connectivity.

Attempted to assign fixed IP's at the router and the PC, still nothing.

Behavior is identical on both pc's, as are results of troubleshooting. Did not reinstall vpn software after uninstalling, DNS flushing and network reset.

As you can see, this is pretty frustrating and I'm unsure as to why this isn't functioning. Any ideas that I haven't tried would be welcome (except completely gutting the OS and reinstalling from scratch...that would suck out loud).