Dropbox is a cloud storage service with which we can upload our work or leisure files whenever we want and wherever we are as long as we logically have an internet connection, however sometimes it can fail giving us errors in copying files for lack of permits or similar.
One of the options that we resort to more times when the applications or the system does not go as they should go, is to open the disk utilities in OS X and select our disk for later click on "Repair disk permissions".
This can work as long as the permissions involved are from system files or application filesSince it does not directly modify anything in our user account, but Dropbox is associated with files in your account, so the developers of this application have decided to "hide" the option to repair specific permissions from the preferences.
To access this option, we will simply move to the Dropbox icon at the top, click on the gear at the bottom right and open the program preferences. In the subsequent menu, we will click on Account and once there we will see how there is the option to "Unlink this computer", but if we hold down the Alt key while we stay in this menu, the option will change to "Repair permissions".
With this it should work perfectly, but if it were not like that we would also have as a last option restart the system while we hold down Cmd + R. When we are in recovery mode, we will go to the utilities menu and we will open the terminal to enter «Resetpassword»When the window to reset the password opens, we will see the option to reset permissions and ACL of the source folders. Now not only Dropbox but any other program with permission problems should work.
More information - Protect your files from other users when you connect an external drive