I’ve seen this issue a couple of times in the past few months where Outlook seems to open and run normally (shows running in taskbar, systray, and task manager) but you can’t see it onscreen.
Basically the issue seems to bee that Outlook is stuck offscreen somewhere, as in on a 2nd monitor that isn’t connected or it’s on your “right” monitor when you’re only using a left monitor.
If you’ve tried outlook /safe to make sure an add in isn’t the cause of your issue and outlook.exe /resetnavpane and neither one has worked, you can try deleting the “office explorer” “frame” reg key. After this is done, restart outlook and get back to work!
The first time I saw this issue the solution involved several steps of doing stuff to force changes to the outlook window’s behavior, and then finally I found this quick one-step fix of deleting the reg key: credit where it’s due- http://lallscreation.blogspot.com/2011/12/outlook-stuck-in-task-bar-opens-off.html#!/2011/12/outlook-stuck-in-task-bar-opens-off.html