I know - the file is locked - but it doesn’t matter if the name servers are not responding - e.g. if they are fenced withing the VPN provider network.
Some old fashioned network trouble shooting may be necessary - to find which name server is actually responding - and why
Maybe it is only the web browser - which may indicate the browser is using the vendor DNS - an annoying method - but more common - the argument is - it prevents a bad UX when the browser don’t load the page.