Thank you for the additional detail.
I uninstalled FTM and then renamed each of these directories. I then re-installed FTM. Unfortunately, still no success. FTM will not launch for me.
This is getting frustrating. My most up-to-date research is in FTM. However, do at least know it is safe as a backup as well. The inability to launch the application is cutting me off from researching, since my online material is not up-to-date since the syncing failed.
I supposed I could use a different User Account, but that is not without its annoyances (and should not be necessary).
I have received an initial response from Ancestry Support, but nothing substantive.
I plan to reformat my laptop in the coming weeks to hopefully resolve this and other bugs. A drastic step, but also the most likely to address the issue permanently.
Thank you again.