Hi s.rebolledo, when you test on your own installation of Firefox, can you determine why the ads are not displayed? I would suspect something along these lines:

Firefox's Content Blocking / Tracking Protection feature and extensions that counter ads and tracking may break websites that weren't built to operate normally without the blocked components.

Do you see a shield icon toward the left end of the address bar, near the lock icon? More info on managing the Tracking Protection feature in this article: What happened to Tracking Protection?.

Extensions such as Adblock Plus, Blur, Disconnect, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix should provide toolbar buttons to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you may need to click the button to see what's going on and test whether you need to make an exception for this site.

Testing in Firefox's Safe Mode: In its Safe Mode, Firefox temporarily deactivates extensions, hardware acceleration, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is not running: Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.)

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" Help > Restart with Add-ons Disabled
• (menu bar) Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any difference?

Thank you for your kind and extensive answer @jscher2000 . Indeed I can make the Google adsense ads to be displayed on my Firefox browser after unchecking the Trackers options on Options>Privacy&Security>ContentBlocking>Trackers... But the thing here is that this solution is only for me and I actually want everybody to be able to see my google adsense ads on my website whenever they are using Firefox browser without having to go to the browser options, just to have the adsense automatically displayed as in the other browsers like Chrome, Opera, IE and Safari... because I dont expect that every user actually go to the Firefox browser options in order to see my adsense ads.

Why do you think Tracking Protection was being applied to your page? Were you viewing it in a private window?

Users who want to block ads linked to tracking by Google have that option in Firefox and other browsers, and as far as I know, websites cannot override it. Some websites refuse to show content in that case, but it may be better to fill the empty space with ads from another provider when Adsense won't load (I don't know how you set that up, but I assume there are tips for it online).