The web whatsapp site is looking for Firefox 115.0 and later to use it. You appear to have the older Firefox 96.0.3 on Windows 7. The latest version of Firefox you can run on Windows 7 is Firefox 115 ESR currently at 115.31.0esr as you can download it from https://www.firefox.com/download/all/desktop-esr/ Just pick the 64-bit or 32-bit Windows, then language then click on [Download ESR 115] https://support.mozilla.org/en-US/kb/how-install-firefox-windows