Some instances have defederated from Lemvotes—including lemmy.ml—which blocks its functionality. Past polls have shown that most Lemmy users do not want votes to be visible, so we will continue do what we can to keep them that way.
If you suspect vote manipulation, I suggest reporting the post(s)/comment(s) accordingly, and let the mods & admins handle them; we can see the votes already, without external tools like Lemvotes.