PDFs not showing in Attach File Panel?

Using EndNote X8, I have saved PDFs as File Attachments. However, when I click on the ‘Attach File’ button on the right hand panel, I am unable to view the PDF and a ‘Select a file to link to the reference’ dialog appears. If I then attach the PDF agian using this dialog (so a second copy is added), once I click out of the reference and save the changes the PDFs are indexed again. But then when I try to view the PDF in the right hand tab I have to go through the same process of selcting a file to link to the reference?

The Attach File icon (paperclip) is a tool to do just that, to attach a file, not to view an attached file.  The PDF “tab” should have a preview of the pdf, or you can right click and choose file attachements,  Open file (rather than attach file, also an option there) to open the PDF in your chosen program (Acrobat Pro in my case).   You can also open the record and double click on the PDF in the file attachments to open in Acrobat Pro (again in my case).  

Thank you - now I feel foolish.