Explanation:

- The sentence is a third conditional, used for hypothetical situations in the past.

- Option 1: "had enjoyed" is in past perfect tense, but it incorrectly implies a completed action.

- Option 2: "would enjoy" is in future conditional tense, which doesn't fit the past hypothetical scenario.

- Option 3: "should have enjoyed" implies obligation or advice retrospectively but is less suitable than "would have."

- Option 4: "would have enjoyed" is correct because it properly follows the structure of third conditionals, indicating a missed opportunity in the past.