What happens when you try to download -- does the site tells you that you don't have permission to access the PDF? One possible reason would be "Total Cookie Protection," a feature that limits how sites can use "third party" or "cross-site" cookies, meaning cookies from different websites than the one you see in the address bar. Some sites pass you back and forth between different servers for different assets, and that could include the PDFs.

You can make exceptions to this feature when needed (for each server that you visit as part of the process of using this company's services). More info in the following articles:

• Introducing Total Cookie Protection in Standard Mode
• Total Cookie Protection and website breakage FAQ

Any difference?

That doesn't help. For all these password protected sites and others, this is the message I get

"filename.rtf "Failed - webpage.com - with the time of the failed download hr:mn

It is the same for filename.pdf and filename.doc

I just tried one of the sites on my phone using Firefox android and it worked, but I don't do this research on my phone.

That message is on the drop-down from the Downloads toolbar button? It's not much to go on. Does Firefox offer any more information if you click that item?

You could check the Browser Console window for additional details:

• Press Ctrl+Shift+J to open the window
• Click the trash can to declutter the display
• Switch back to your tab and trigger the download again
• Switch back to the console and check for any new information

What I get after following the steps you suggested is in the attached file.

That looks like problems with background files from extensions.

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

I noticed that the list was filtered to show only "Errors" but it seems there might be a Warning as well. Maybe you checked that and it didn't seem related to the problem.

As it turns out, the solution was pretty simple. After I tried all of the suggestions, I changed default for downloads to a new folder on my computer and set Firefox so that I need to choose the folder where downloads will go.

Thanks for everyone's suggestions.

Thank you for reporting back. It doesn't really make sense that some sites could download to the previous folder and some others couldn't. But, not all mysteries need to be solved to get work done.