For whatever reason, the option to set up an alert for new comments on a review is no longer an option. You can try setting up an alert on the review page by clicking on the bell icon on the left side. If there is not the option for new comments, try selecting any of the choices. Then, go into your account under "Promotions and other alerts" and select your review alert that you just set. Try to edit the alert and see if it gives you the option for new comments. Otherwise, you will probably have to submit a support ticket.