Renamed Home Folder, now Dropbox Mac App won't launch
Dropbox support got back to me, and had a fix. Not simple so open up your terminal. 

Please save and quit all programs accessing files in the Dropbox folder, and then follow these instructions:

Note: Please be sure to take note or take a screenshot of any Selective Sync settings you may have applied prior to re-installing in case you need to re-apply these settings upon re-install.


Stop Dropbox (If needed):


Click the Dropbox icon in the menu bar at the top of your screen
Click on the gear icon in the Notifications panel and select 'Quit Dropbox'

Download the newest version:


www.dropbox.com/install


Open your Terminal app (Located at /Applications/Utilities/Terminal)
Copy and paste the following lines into the Terminal, ONE AT A TIME, and press ENTER after each one. PLEASE make sure you copy and paste these commands (don't type them by hand), as getting them wrong could cause some harm. You'll be prompted for your computer's admin password (not your Dropbox password) after entering the first command. Keep in mind that the password field in the terminal will remain blank as you type your password. After you type it, just press ENTER.


sudo chown "$USER" "$HOME"

sudo chown -R "$USER" ~/Dropbox

sudo chmod -R u+rw ~/Dropbox

sudo mv ~/.dropbox ~/.Trash/dropbox.old

sudo chmod -N ~

sudo mv /Library/DropboxHelperTools ~/DropboxHelperTools.old

(Note some of these commands didn't actually do anything. I think they were just trying to be super thorough.)


Open the .dmg file from step # 2 and double click the Dropbox icon to install Dropbox.
Restart Dropbox from the Applications folder, then please sign in and apply any Selective Sync settings you may have had prior to the reinstall during the sign in process. Your account will take a few moments to reindex the files and sync any pending changes.