Hi, I do not think support has ended for it and the Developers site is still up https://addons.mozilla.org/en-US/firefox/addon/icloud-bookmarks/ Please check with the Developers Support Page and Contact if have to see if they have seen this issue. They last updated it 4mos ago. All solutions I have will end up having you locked out of sync and having to request access from bugzilla and provide the details. So it would possibly be best to start where having the issue then work this way. As I would suggest this : Refresh but Note that this does more than uninstalling and re-installing does. Normal uninstalling does not remove some preferences which may have become corrupt. Please Refresh but do this 1st: Delete your Cookies and Cache and TEST. *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles then *https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings TEST....... If no issues then Extensions which need to be added back in 1 at a time and tested ..... Or it is your Profile : Make a new one and test ...: *https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles If is your Profile : *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox Note: Any customization will revert back to default, you will also need to reinstall Extensions. Please let us know if this solved your issue or if need further assistance.

Thanks a lot for your help. Simply deleting all COOKIES already solved the sync problem. It now works fine again. So simple a sulution, yet so hard to see ...! Cheers from Munich.

Just as a note...iCLOUD set-up still says FF not installed, but I d'ont care, sync works.