Menu items in EndNote may not be available depending on which mode is selected in the Library window:
When Local Library Mode (the default option) is in effect, EndNote displays automatic groups, custom groups, and smart groups, but not Online Groups. It keeps you from inadvertently downloading references found during an online search into your currently open library.
When Online Search Mode is in effect, the only groups available in the Library window are Online Searches, as well as the automatic groups “Online References” and “Online Trash.” You cannot save changes to individual references or make global edits in the library.
For a full description of the three modes, see The Library Window Display Modes.
Commands may also be dimmed depending upon which part of the window is active. For example, if the Groups panel is active in the Library window, and no reference is selected in the reference list, the Edit References command will not be available from the References menu. It would not make sense in this context, since there is no reference selected.