Key Photo for Album Cover - Photos app iMac
I am using an iMac OS X.
I have moved my entire library from iPhoto to Photos on my iMac.
I see the menu item for Key Photo (to change the one I see on the album cover) but am not able to select it. Whether I select Photos or Albums, it is always grayed out. Why?
I do not have my pictures on iCloud and am just wanting to change the cover of the album photo.
iMac, OS X Yosemite (10.10.3)