Firefox, since version 77 with enhanced tracking protection enabled blocks Google Adsense ads by default, probably also in conjuction with 3rd party cookie blocking.
That’s like a declaration of war from Mozilla to Google.
*grabs popcorn*
update: actually it’s not Firefox 77. It’s me, blocking the google.com cookie domain. Nice side-effect, no access to google docs as a guest, no reading youtube comments, and many more.