I'm not sure if this is just me but I can't access aetherii.com at all through any browser.
I tried google chrome and firefox. I can ping it just fine in my terminal window. I am using cloudflare's DNS service 188.8.131.52 thing... is that an issue lol?
aetherii.com doesn't exist anymore, it's been in development hell forever. You can go to the curseforge page for Aether II and join the discord however, that's where all the activity is. There's also the Gilded Games twitter you can follow for updates.