BUG. Spent days on this.
Installed latest release of RStudio, but starting gave me no window, no panes.
Menu bar seemed normal.
Tried selecting the window from the RStudio icon in tray or from the Window menu. Nope.
Deleted all .Rprofile, .RData, .Renviron, still no joy.
Worked through all R installations on my machine thinking RStud couldn't start R.
Environment variables right. R runs in terminal fine.
Touched menu Window->Zoom and it appears.
Turns out new installation started window Minimized, yet normal selection of window from tray icon didn't Maximize.
After window was Max'd once, all selection seemed to work as expected.
R version 3.4.4. RStudio Version 1.1.442. MacOS High Sierra Version 10.13.4