I just upgraded to Fedora 27 (from 26) and they removed the system tray in this version.
I performed a test by adding a new file and it seems insync works and the file was uploaded to Google Drive
But still a method of knowing the sync status is needed.
If you install the TopIcons Plus Gnome Shell extension from here: https://extensions.gnome.org/extension/1031/topicons/ you will be able to see the icon (also the Skype and Dropbox icons if you use those tools as well)
I do have TopIcons Plus installed, but it doesn’t show insync icon when I login to a new GNOME session, even though the process is running and healthy (it reports “SYNCED” to “insync get_status”). I have to manually restart it (insync quit && insync start) so that it appears on the top status bar. It doesn’t seem to be a problem with TopIcons Plus because other apps (eg. SELinux Troubleshooter) appear just fine.
One thing I’ve noticed is that with the Top Icons Plus extensions I don’t see the tray icon when first login but the process is running. You can run the command “insync get_status” to verify.