Proton VPN advised me to switch to a different server when one is blocked by a website. That usually works for me. I haven’t had the username and password problem though. I think the only sites I’ve had to turn my VPN off for were credit reference agencies.
https://web.archive.org/web/20240419051951/https://www.moneycontrol.com/news/technology/swiss-authorities-intervene-proton-mail-not-blocked-in-india-12672231.html