Desktop items disappearing because of new Dropbox update
If your desktop items are gone and you're receiving this error upon opening File Explorer, your desktop items have been syncing to Dropbox and their update has changed the location of your desktop (and other) files/folders.
This issue is most likely affecting your Desktop, Documents, and Downloads folders. Here's how to get your items back.
1. Open File Explorer. 
2. On the left side of the window, there's "Quick access" and associated folders listed. Under that, there is a new location named "Harley Marine Dropbox" which was formerly "Dropbox (Harley Marine)". Navigate to Harley Marine Dropbox > Your Name.
3. Inside that folder there will be your Desktop, Documents, and Downloads folders along with other folders/files. There may be duplicates of these folders. Open each folder and find which one has your files.
If you are comfortable doing so, delete the folders that don't contain your files.
4. Inside the correct Desktop folder (and later, for the Documents and Downloads folders if necessary) use the address bar at the top to copy the full location of the folder.
5. In the "Quick Access" section on the left side, Right-Click the "Desktop" folder and go to Properties > Location Tab. Paste the copied address into the text field and Press Apply. On the prompts that follow, choose Ignore All, and then Yes.
6. Repeat these steps for the Documents and Downloads folder if trying to go into those folders yields the same error. Reboot the computer when you're done.