The analysed Firefox version is 125. If you have another version it’s maybe different.
Desktop
You have to add your country to the supported countries list.
Workflow
1. Open page “about:config”
2. Request “extensions.formautofill.addresses.supportedCountries”
3. Add your country code (e.g., “US,CA,GB,FR,DE,IT,ES,AT,BE,PL”)
Mobile (Stable release: Doesn’t support about:config)
You have to switch the language to en_US, en_CA or fr_CA.
Workflow: “Setting” → “Language” → “English (United States)”