For people who, like me, are having trouble with insync running but not showing anywhere on GNOME’s top bar (despite all the hacks with extensions etc.), here goes a tip that might make your life a little bit easier: try assigning “insync show” to a keyboard combination. I just assigned it to ALT+I, and even though I miss being able to quickly glance at the tray icon to see what is insync’s status, at least now I have a quick way to interact with it and, in my experience, it makes a difference (YMMV).
Hope it helps.