Not sure about question 1 – can you find it in the library and insert it from there?
2. Can you convert the citations to temporary (unformatted) citations from the Endnote toolbar, and see what they look like?
If your “formatting” preferences (in Endnote) are set as shown in the attached image, then leaving an author or year out of the temporary citation will leave them out of the citation in the text, but if you untick that box then the full citation will apear in any case. The ticking or unticking of the box will not override the @@ settings for Author (Year) (@@author-year) or “show in bibliography only” (@@hidden)
Not sure why you don’t have the option to choose Author (Year) unless they are a group of citations, which are greyed out-- but you can do it - from the more and select each one and choose that option. (image 2)
The options are complicated, but see below
Author (Year)
{Zhu, 2010 #5505@@author-year} which will appear Zhu (2010) irrespective of preferences settings and doesn’t work well in a “group” of citations
Just year
{, 2000, #1079} which will appear (2000) no author unless you untick the box in preferences settings shown in the attatched image, then (Smith, 2000) “Smith and his colleagues showed this and that (2000).”
Just Author
{DeAntoni, #974} which will appear (DeAntoni et al.) unless your untick the box in preference settings, then (DeAntoni et al., 1997) For a sentence like “In 1997, there was a report demonstrating this and that (DeAntoni et al.).”
Show in bibliography only
{Parker, 2017, #12@@hidden} which will remain hidden irrespective of the ticked box status) (not sure when you would want to use this though).
no author or year
{, #3896} on it own will format (Uehara et al., 1988) but in the middle of a group, it will have a trailing extraneous close parenthesis unless you modify the citation template I think. - so better to use the @@hidden option. but ditto, don’t know when you would want to list a reference not used in the paper.