Curiously, I get a 403 if I try curl …
Craigs-iMac:~ craig$ curl -I https://www.hinz.org.nz/resource/rss/news.rss
HTTP/2 403
date: Wed, 11 May 2022 14:04:59 GMT
content-type: text/html
content-length: 1233
x-datadome: protected
accept-ch: Sec-CH-UA,Sec-CH-UA-Mobile,Sec-CH-UA-Platform,Sec-CH-UA-Arch,Sec-CH-UA-Full-Version-List,Sec-CH-UA-Model,Sec-CH-Device-Memory
set-cookie: datadome=EU3BHAFHQ05_KVgwW1Wjs9oOG7yBN6ViNb-Z0zhemMzTdky84_xqOxGy~PCdj6GF2paWbjlV6YBVr8EffwN.eBXFJjRmcsp9ix7FLkAxA2yCry0Eo6sLlqchK2zbnjV; Max-Age=31536000; Domain=.hinz.org.nz; Path=/; Secure; SameSite=Lax
location: http://www.hinz.org.nz/resource/rss/news.rss
x-powered-by: ASP.NET
referrer-policy: no-referrer-when-downgrade
strict-transport-security: max-age=31536000
x-xss-protection: 1; mode=block
x-content-type-options: nosniff
Maybe that server is picky about user-agents? …if the RSS validator can fetch it, but my curl, and the plugin cannot . . .