I'm sorry to hear about this. If you're not on a Dropbox Basic plan with more than 3 devices connected, could you try uninstalling the mobile app, rebooting the phone, and reinstalling it to see if this helps?
"Generally, offline files are inaccessible outside of the mobile app, so having apps directly access the folder where they're stored isn't something that's supported by Dropbox."
That's how I've been accessing my mp3 files stored offline on my Dropbox for years. The mp3 app I use to play podcasts would look for the offline mp3s under Android/com.dropbox.android/files/uxxxxx/scratch. Now, with version 200.2.8, It can no longer access any of my offline mp3s.