The game itself works fine, but it can't access the leaderboards at all, and my high score isn't saved. The main page says "server connection failure" and "failed to load rankings" in the leaderboards. Are the servers still down in some regions? I tried repairing the game in Galaxy and deleting %APPDATA%\Nex Machina.

I figured this out myself: I had a virtual switch configured in Hyper-V's Virtual Switch Manager (in Windows 10 Pro). I removed the switch, and now the game can access the network.

Surely this is a bug, and not intended? This is the first game I have that doesn't like virtual NIC's.

The latest update solved this for me. Sorry for accidentally clicking solved in your post, I can't undo it.

I'm seeing this problem after installing new just a few minutes ago (just purchased), with the GoG version. I have Hyper V, but it is not enabled at all. I allowed the game .exe in Windows firewall and tried turning off service blocking on my router, to no effect. Are there any other fixes for this?

I hadn't realized the game must be installed through GoG Galaxy for online leaderboards and the Arena to function. Reinstalled using GoG Galaxy fixed my issue.