sync iCloud contacts (including groups) to Thunderbird

I am working on a Mac mini 2018, with Sequoia 15.7.5 installed, with Thunderbird 156.0 installed as my e-mail client. Every year about this time, I have to update the members of a couple of groups. This has always smoothly worked if I make the changes in iCloud's contacts, then wait a couple of hours and it syncs to Thunderbird. Not this year. No changes occurred. I have (more than once each) removed the iCloud address book and attempted to reinstall by creating a third party app password (Thunderbird freezes up after I enter username, URL and password and won't let me go further); closed thunderbird and reopened; uninstalled Thunderbird and reinstalled; attempted to export my iCloud contacts and import them to Thunderbird (nothing happened). At this point I'm worried I may have to manually enter a whole new address book for Thunderbird by hand. That would likely be several hundred addresses. Anyone have any suggestions?