OG metadata / link previews not working in some apps

Since a few weeks ago, link previews are no longer working when I post links to any of my Workers or Pages sites in certain apps---most notably Slack and Lucid (https://lucid.co). Link previews worked fine in these apps before, and some of my sites I haven't changed since months ago. Link previews in other apps (LinkedIn, Facebook, Mattermost) all work fine. I cannot for the life of me figure out what is going on. 🤔 Any ideas?