Try to go to about:config and add your country code to the extensions.formautofill.addresses.supportedCountries preference.

Thanks. The country code is already in. I did find that this line:

extensions.formautofill.creditCards.os-auth.locked.enabled false

is showing as false, but it also shows as locked. I cannot acces it by double tapping. Am I on the right track? If so, how can I unlock this to change it?

WARNING from the moderator team: Changing Firefox preferences from the about:config page can sometimes break Firefox or cause strange behavior. You should only do this if you know what you're doing. Please read Firefox advanced customization and configuration options to learn more.

Is this a version of Firefox you have downloaded and installed from Mozilla?

As far as I know. It has been working fine for me for years until I replaced the iMac last week.

I see your warning and am heeding it. But, it seems like there should be some way for me to get the credit card autofill feature back. Anybody have any suggestions?