"Service Unavailable." troubleshooting

[juju4]

There are multiple feeds that I can't add for miniflux. It returns Service unavailable (repeatedly) but manual browsing or server curl works normally.
How to get more details on the error?

Examples:
Miniflux is not able to reach this website due to a network error: Get "https://www.joyoftech.com/joyoftech/jotblog/index.xml": Service Unavailable.
Miniflux is not able to reach this website due to a network error: Get "https://techcrunch.com/feed/": Service Unavailable.

Thanks