I'm a dummy.
I downloaded the game and the launcher separate from the downloads tab. I misunderstood the instructions and thought running the launcher would handle everything (that's the one that inspired this thread).
But I didn't run the actual game setup (hence why I'm a dummy). So I ran it, then tried to run the separate launcher and got the SAME failure message. So I thought it was because it was still a separate folder. So I copied the launcher file into the game folder. And it STILL failed. But I noticed the game folder had its own launcher.exe.
So I deleted the game, re-installed, and ran the launcher.exe that was already in the game folder (not running the separate launcher) and it worked fine and can now log in.