If EndNote has not found and attached a PDF to your citation, you will have to attach it manually.
1) Select the citation that does not have a paperclip.
2) Click the OPEN URL icon.
3) See if there is a PDF available, you might have to press the FINDIT@MU button.
4) Download the PDF
5) Select the citation you wish to attach the PDF to.
6) Click the PAPERCLIP (on the right hand side where the metadata is kept),
browse to the downloaded PDF and select it.
7) Click on another citation and when prompted, click SAVE CHANGES.