Hi. I have just solved my similar problem – I had updated to 3.9.2 and also added a new theme and couldn’t get either the “text” or “visual” tabs to show on the page/post editor. Tried changin themes, disabled then deleted all plugins, updated php on my hosting. Was stuck! Then saw soething about users so checked and I have 2 admins and was logged in as one I hardly ever use (don’t know how that happened) and upon check his roles the “disable the visual editor when writing” was checked. Unchecked and all working !! Hope this may help someone
