ActionText saving rich content, but not uploading embeds

Question

ActionText/Trix will store rich text, but will not process/store embeds either locally or on S3. When I drag a file into The progress bar on drag/drop does not progress, but the image shows up and the filename and file size are accurate, as seen here:

A regular ActiveStorage attachment on the same model works fine, uploads to S3, etc. so I've ruled out ActiveStorage as the culprit.

Debugging wise:

• There are no errors reported in console (Safari or Chrome)
• I did find a variety of posts here on SO with somewhat similar issues, and I tried two primary solutions (re-run rails app:upgrade and ensure CORS is good to go on S3 bucket), however, neither has changed the outcome (file still does not upload directly).
• This behavior persists in Chrome and Safari, and there are no console errors. The blob in the Network tab shows up as a 200 status.

Application wise:

• JS is loaded by importmaps, and trix and action text are required in the application.js file.
• The application is Rails 7.0.6 on Ruby 3.2.2, but this is an older Rails app that's been through some upgrades (started on 5.x).