Some time ago, Ancestry changed their URL structure, making all old links no longer valid.
Often, though, there is still enough information in the old link to reconstruct it into a proper new link. (and there is a template one can use to make that task easier).
Unfortunately, sometimes the links are just simply no longer valid, due to closed accounts, etc.
If its possible to repair the links (or replace them with something else equivalent), this should be the preferred course of action.