@peterbb You shouldn't need, but for some reason the installer wasn't being able to connect to Opera servers to download the browser, and using the offline installer is a workaround.
Found the link for the offline installer in another thread and was able to update opera. Still not fully functional. Still getting you're offline and network connection error messages.
@enhtity I am having the same problem, but I just log out of my school opera account and log back on to my personal opera account. It can take a couple of seconds, but it's worth it after all.