Another workaround from http://askubuntu.com/a/739018/506976 for the current Dropbox tray icon bugs that is reported to work at least on the Linux distributions Fedora, Kubuntu, Linux Mint, openSUSE, Slackware, Ubuntu... and the desktop environments Cinnamon, KDE 4, KDE 5, Mate, Unity... is the command line:
Another workaround from http:// askubuntu. com/a/739018/ 506976 for the current Dropbox tray icon bugs that is reported to work at least on the Linux distributions Fedora, Kubuntu, Linux Mint, openSUSE, Slackware, Ubuntu... and the desktop environments Cinnamon, KDE 4, KDE 5, Mate, Unity... is the command line:
dropbox stop && dbus-launch dropbox start