You can check the extensions.formautofill prefs on the about:config page. You can open the about:config page via the location/address bar. On the warning page, you can click "Accept the Risk and Continue" to open about:config.

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

• extensions.formautofill.available = "on" (String)
• extensions.formautofill.addresses.enabled = true (Boolean)
• extensions.formautofill.creditCards.available = true (Boolean)
• extensions.formautofill.creditCards.enabled = true (Boolean)
• extensions.formautofill.creditCards.hideui = false (Boolean)

Close and restart Firefox after changing these prefs.

I can't find several of the options mentioned, e.g., .extensions.formautofill.creditCards.hideui These are in my about: config extensions.formautofill.creditCards.available true extensions.formautofill.creditCards.enabled true extensions.formautofill.creditCards.heuristics.fathom.confidenceThreshold 0.5 extensions.formautofill.creditCards.heuristics.fathom.highConfidenceThreshold 0.95 extensions.formautofill.creditCards.heuristics.fathom.testConfidence 0 extensions.formautofill.creditCards.heuristics.fathom.types cc-number,cc-name extensions.formautofill.creditCards.heuristics.mode 2 extensions.formautofill.creditCards.ignoreAutocompleteOff true extensions.formautofill.creditCards.supported detect extensions.formautofill.creditCards.supportedCountries US,CA,GB,FR,DE extensions.formautofill.creditCards.used 3 extensions.formautofill.firstTimeUse false extensions.formautofill.heuristics.enabled true extensions.formautofill.loglevel Warn extensions.formautofill.reauth.enabled false extensions.formautofill.section.enabled true extensions.formautofill.supportRTL false