Jonathan, links to ancestry sites are hidden for many people now because of ad blockers, since they are automatically redirected to the page to either login if you're an ancestry member or purchase a subscription if you're not.
The link isn't the problem, though. The citation indicates that it is an ancestry tree. Many actual records are available at ancestry and these are excellent sources, despite the problem of being behind a paywall. Ancestry trees, however, are not considered valid sources of anything. Anyone can put anything they want on their ancestry tree and after that, it seems to acquire a life of its own, being copied over and over into other people's trees. This does not make the information any more valid, though. Ancestry (or any other online) family trees are not acceptable sources for pre-1700 profiles. I believe that's one of the things in the certification quiz.