Enfranchised is the past form, and also a describing word. If a group was enfranchised, they were given the right to vote. You can say “women were enfranchised in that year,” or talk about “enfranchised citizens” — people who already have the vote. It has the same serious, political flavour as enfranchise; it belongs in history and law, not in daily chat. It does not mean “allowed to speak,” and it does not mean someone who runs a shop franchise.