Sorry to hear about this problem. A few versions ago, the "scissors" icons was removed from the address bar and became an optional toolbar button. You can find it among the available buttons in the Customize panel and drag it to a convenient part of the toolbar. More info on that panel: Customize Firefox controls, buttons and toolbars.

Two other methods for triggering Firefox Screenshot are:

• right-click a blank area of the page > Take Screenshot
• press the keyboard shortcut Ctrl+Shift+S

If none of those is working, please check whether the extension got disabled this way:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste extensions.screenshots.disabled and pause while the list is filtered

(3) If the preference is bolded and has a value of true, double-click it to restore the default value of false

More info on about:config: Configuration Editor for Firefox.

Any progress so far?

Thank you so much sir @Jscher2000 for the tips, it was indeed helpful. I thought it was hopeless for the new update. Now i can screenshot anytime :)