See this support article:
https://support.mozilla.org/en-US/kb/automatically-fill-your-address-web-forms?redirectlocale=en-US&as=u&redirectslug=automatically-fill-your-address-and-credit-card&utm_source=inproduct

And this wiki page and paragraph:
https://wiki.mozilla.org/Firefox/Features/Form_Autofill#Feature_Availability

You probably need to turn that feature on with non-US builds.

The new Form Autofill feature is rolled out gradually starting with Firefox users in the US. Others can enable it by modifying some prefs via the about:config page. Close and restart Firefox after changing these prefs.

• extensions.formautofill.available = "on" (String)

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox