It basically says the network is blocked due to malicious behavior, and can not even do the captcha because it always fails even when doing it correctly.
I dont know if this happens with every country server, but at least with Brazil servers, it always happens and its annoying.
Also, I am argentinian. Closest thing to Argentina is Brazil, theres nothing closer than that, because Mullvad got no servers here, and I dont know how to request them.
If captchas are failing then it is likely your browser: you probably have scripting turned off, or a blocker is active, or some such. Nothing to do with your connection.