Opening links to PDF files

In the past, when I've clicked on an Internet link to a PDF file, the file just opened (using Win10, Firefox browser and Foxit reader), but now, when I try and open an Internet link to a PDF file, I'm asked where I want to save it. How do I get back to the file just opening? Foxit reader is my default PDF reader in settings>choose default apps by file type. I've also set Foxit reader to be the default application in Firefox Tools>Options>General>Applications PDF files already on my computer, selected with Windows Explorer, open quite normally.