You'll have to contact whatsapp support to find out why their current app isn't working with latest Firefox.

In usual mode WhatsApp web works well, it's not working in private mode, I'm pretty sure problem is in browser.

Are you possibly using Private Browsing mode or made other changes like enabling "Resist Fingerprinting" ?

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history
• https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting

Having GPC (Global Privacy Control) or DNT (do-not-track) enabled also can cause problems.

Are you possibly using Private Browsing mode or made other changes like enabling "Resist Fingerprinting" ?

• https://support.mozilla.org/en-US/kb/private-browsing-use-firefox-without-history
• https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting

I checked all the options, tried to disable all the blockers but nothing helped. I use Private browsing when I face this problem

Having GPC (Global Privacy Control) or DNT (do-not-track) enabled also can cause problems.

Both options are not enabled