I’ve seen the question asked and answered a few times in-thread where it quickly gets buried by followup posts, so wanted to put this out in the open by itself.
When editing old posts you’ll see some images are either appearing as unembedded links or else as broken embeds. The broken embeds are down to a 429 error, i.e. imgur has received too many requests from our site. shane has advised that, when possible, we upload images here, to Discourse, since imgur embeds have a shelf life even when there isn’t the 429 error.
When editing an old post, open the link that was transferred here, copy the image to clipboard (or save to your computer, if you want) and paste/upload again so Discourse hosts the image.