Explanation:

- The original segment "you not watching it" is incorrect because it lacks proper verb agreement for present continuous tense.

- Option 1: "do not watching it" is incorrect because "do not" should be followed by the base form of the verb ("watch"), not the -ing form.

- Option 2: "No substitution required" is incorrect because the original phrase lacks grammatical correctness.

- Option 3: "did not watched it" is incorrect due to the improper use of past tense for a present continuous context.

- Option 4: "are not watching it" is correct. It uses "are" for the subject "you," which is appropriate for present continuous tense to indicate an ongoing action.