@Juanjo: This is the way I solved the issue with Dropbox in Ubuntu MATE 17.10 (should also apply if you upgrade to Ubuntu MATE 18.04): Caja Dropbox not showing popup menu after starting (Mate 17.10)
@Juanjo: This is the way I solved the issue with Dropbox in Ubuntu MATE 17.10 (should also apply if you upgrade to Ubuntu MATE 18.04): Caja Dropbox not showing popup menu after starting (Mate 17.10)