In Civi 5.26.1, I've just had a user tell me that a registration page doesn't work because there is no 'Continue' button.
Indeed, although the on-page instructions state "If you are registering additional people, you will be able to enter their registration information after you complete this page and click Continue", the only button available says 'Review you registration'.
Suggest that the relevant string in Register.tpl is amended to 'If you are registering additional people, you will be able to enter their information after you complete this page and click Review Registration'