https://blog.imgur.com/2019/10/14/discontinuing-support-for-nsfw-reddit-subsections/

TL;DR Imgur is now blocking NSFW content from being viewed by anyone not logged on to Imgur. Since the vast majority of our users aren’t logged on Imgur (and probably will not go through the effort of logging on just to see your pics) almost no one will be able to see your pics.

It’s best to stop using Imgur altogether, since it’s highly likely this is the first step towards the complete removal of NSFW content, like Tumblr. Alternatives are to directly upload your pics to Reddit or use Erome. If you insist on using Imgur, you must link directly to your image or else no one will be able to see it. Make sure your link ends in a filename format, i.e. imgur.com/example.png instead of imgur.com/example or imgur.com/a/example.