Imgur blocks access to most VPN IP addresses so any posts using the host will result in many users being unable to see the content. Sometimes only remote viewing is affected but is also often blocked when trying to open in new tab and view at the parent site.
Consider uploading to the fediverse or using a privacy-respecting hosting service like postimages.
It sounds like that’s some network providers that block catbox, rather than vice versa.
https://catbox.moe/faq.php
Probably the most significant ones on there from a standpoint of users here are “Australia”, “Rogers”, “Comcast”, and “Verizon”. It sounds like all of those blocks are pretty easy to bypass (like, they’re either DNS-level or can be disabled by users on their router, where there’s a blacklist toggle that’s on by default).
I’ve never once even managed to get anything from Catbox via Tor, via different routes. Seems to be a rather widespread problem.
They must’ve hosted something egregious to make a whole bunch of ISPs and entire countries block them.