Fairness in Medicare Part B Enrollment Act of 2021 This bill exempts an individual from late-enrollment penalties for Medicare medical services if the individual resided in Puerto Rico as of the date of eligibility and the individual enrolls within five years of such date. Currently, the late enrollment penalty is 10% of monthly premiums for each 12-month period during which the individual was not enrolled, and the penalty continues to apply for as long as the individual is enrolled in Medicare medical services.