Imgur now blocks several VPNs and have issues loading embedded previews in several fediverse platforms. So instead of using imgur, you could use one of the following alternatives for uploading your images.
https://postimages.org/
https://imgbox.com/
https://imgbb.com/
https://www.imagebam.com/
There are files I’ve uploaded to them since their service started that are still there.
After a while, files go into a “cold storage” and there’s a wait until the server retrieves it.