Dropbox context menu missing in OS X

In this thread, the person reported that Context menu is shown upon restarting the computer. can you please try that?

of course after install/reinstall :-).

Common fix to missing contextual menus in macOS: Confirm that the "Folder Actions Setup..." service is enabled in System Preferences.

System Preferences -> Keyboard -> Shortcuts -> Services -> Files and Folders. Make sure "Folder Actions Setup..." is enabled. (This has worked since Mac OS X 10.6.8, tested again in macOS 10.13.6)

Original info source: https://forums.dropbox.com/topic.php?id=16490&replies=18#post-104122 (link is now broken)

NOTE: This step was already attempted by the OP, as indicated in their initial question. I'm including this answer anyway, since taking this initial first step is what instantly brought back my Dropbox contextual menu (and others). It could be a helpful first step for someone else missing their context menu, so I request my answer to be left in as a quick reference for future user queries.

I had the same problem and found that if I quit and restarted the Dropbox application it would work again.

I found that sometimes I would reboot/log out and in and it would work, other times a reboot/log out wouldn't help.