Our recommendation at the library, and EndNote's support position, is that EndNote's "Find Full Text" is variable in its performance, and not always the most reliable way to find library-subscribed PDFs.
We suggest you always use it in conjunction with Endnote's OpenURL linking feature: if you right-click the citation and select “URL—OpenURL Link” you have much better success than you do with Find Full Text.
To use Find Full Text:
3. For every journal article that was “Not found” in step 2, right-click on the citation and select: URL —> OpenURL. This will open a link to the PDF, if available.
4. Save each PDF, or follow the prompt to order Interlibrary Loan PDFs if we don't have the item.
5. In Endnote, individually attach the PDF files that you got in step 4 using right-click (control click on the Mac) and Attach File to the citation.
Faculty may have an additional option: installing the campus VPN may give even better Find Full Text results.