Have you tried other websites? Have you tried another device? If it works on other websites, it may be because the website actively prevents "printing" when the pages appear blank.

yes, it doesn't work on any sites.

Print buttons may do a variety of different things, but two of the most common are:

(1) Pop up the built-in Print dialog using the window.print() script function

This might not work in mobile versions of Firefox. I tried the buttons on two different test pages and nothing happened.

(2) Pop up a new window (tab) with a print-optimized layout

User-initiated popups should work, but then, any automatic printing script in the new tab might not do anything (see #1).

What if you try either:

• menu > Page > Print (not present on all devices?)
• menu > Page > Save as PDF