FTM for Mac will only work on Mac computers
I was suggesting that you try it on another Mac.
If it works, then you know that you don't have a problem with FTM or Ancestry but in your Mac computer. There are settings etc that can be adjusted.
My other thought is that syncing and linking involves of course the Internet and how you have set up your internet, firewalls, virus checkers, and the like.
Again, if it works on another Mac again you know where to look.
It is up to you to decide if you won't to elimintae some unknowns or not, or simple play around with your file hoping. me, I would try and work through the variables until you pin point the issue
If you want to continue with your file and assume that your computer or more accurately its settings are ok, I would suggest this
Create a new file on FTMM with one person, yourself.
Now merge you main file to this file and then remove the simnge duplicate.
Now try linking and syncing.