In case you have the same problem:
I just rebuilt my Dell W7 64bit and I added EN for Win. The Outlook EN icon was not present.
When I opened Outlook>Options>Add In Window, EN did not appear. When I opened the Com Add Ins window, Evernote.Outlook appeared.
I clicked on the add button and it took me to Users>Jay>AppData>Roaming>Microsoft>AddIns. Nothing was there.
When you highlight Evernote.Outlook in the Com window it indicates that the file is at Program Files (x86)\Evernote\Evernote\EvernoteOL.dll
Not having any idea whether what I was about to do would work I copy and pasted the .dll into the MS Addins folder.
I closed and opened Outlook and the EN button now appears!!
Guess What? When I open the MS Addins folder - there is nothing there!!
I have no idea what I did tht caused the button to appear - it is just there and tested and working.
Perhaps one of the EN Mods can explain.