"Are you sure you want to delete this file" error message

• Delete files or folders from a shared folder
• Delete files or folders from your Dropbox account
• Move files or folders from a shared folder to a location that other members of the folder can't access (like a private folder or a folder not in your Dropbox account)
• Move files or folders out of your Dropbox account

If you didn’t mean to delete or move these files, click Cancel. If you want to confirm the delete or move, click Delete or Move. 

If you’re deleting files to save space on your hard drive, try using selective sync or setting your files to online-only instead. 

How to undo accidental deletions on macOS 10.15 (Catalina)

To undo accidental deletions on macOS 10.15 (Catalina), you’ll need to enable Full Disk Access. Full Disk Access gives Dropbox permission to undo accidental deletions. 

To enable Full Disk Access:

1. Open System Preferences and click Security and Privacy.
2. Click the Privacy tab.
3. In the bottom-left, click the lock icon to make changes.
4. Enter in your computer password and click Unlock.
5. Scroll down to Full Disk Access and check the box next to Dropbox.
6. Click Quit Now to quit and restart Dropbox.