Airport Extreme A1301 Blocking Windows File Sharing Through Ethernet?

I use a Google Nest Wifi Pro as a router and access point. I connect the LAN port on the Nest to the WAN port of my old Airport Extreme A1301 - with all wireless and networking features OFF - and use it as a gigabit switch to connect my Mac Studio and a Workstation PC via ethernet. Connected this way, I consistently get 1gig down- and upload speeds through Google Fiber Webpass. It's slower if I connect via Wifi, so I prefer for these desktop machines to be wired.

However, I am having issues with network file sharing, and it seems like the PC isn't playing nice with the AE. If I disable the ethernet port on the workstation PC, and connect through wifi instead, everything works fine, but with identical settings I cannot get "Connect to Server..." in Finder to bring up the login credential box. Literally the only difference is the PC connects to the Nest wirelessly instead of the AE through ethernet. All other settings are the same in Windows.

YES, I have read this: Connect to a Windows computer from a Mac - Apple Support (KZ)

There aren't many options or preferences to edit when all wireless and networking features are off on the AE, so I'm not sure what else to do here. Is it possible that the AE is just incompatible with Windows file sharing through ethernet and will never work? Is there a special setting I just don't know exists?

Is it possible that this is a setting in the Nest? I'm not a big fan of the UI for managing the Nest, since I have to do it on my iPhone, so I've been putting off exploring that part. Also, my Mac Studio has been wired through the AE when the workstation PC was on Wifi and filesharing worked, so I am skeptical that the Nest has anything to do with this. But, I am willing to be convinced!