What happens when you try to open the statement? Is there an error message?

Two thoughts come to mind:

(1) Many statements open in a popup window

Usually Firefox allows popups that directly follow clicking a link or button, but some popups are blocked. Do you see any messages in the toolbar area related to a blocked popup?

(2) Many statements are in PDF format

Usually Firefox will display PDFs in a new tab. If you get a blank tab, it could indicate that the built-in PDF viewer is disabled.

No I don't get any error message. It tries to open the requested statement but only for a second, then nothing happens. This is happening on all websites where I try to open a pdf I don't get any indication that a popup has been blocked and no new tab opens

Could you check your Downloads list to see whether Firefox is auto-saving the files instead of opening them? It should be accessible from the Downloads button on the toolbar.

If you need to override that behavior, you can select Open in Firefox on the Settings page: View PDF files in Firefox or choose another viewer.

I think I fixed it. I opened up my list of downloads (CTRL-J) and went to one of my previously downloaded PDFs, then right clicked on it and selected "Always open in system viewer". Now I'm able to open all PDFs on sites. Thanks so much for your assistance but I guess I accidentally stumbled on the solution!

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.