My son cannot access his Meta Horizon account in order to use his Meta Quest 3.

Hi, my son has been happily playing on his Meta Quest 3 for a year and suddenly has been locked out of his account (which is a child’s account with me as the parent). When he enters his email, no code is sent and an error message appears on the Meta app. We have tried on multiple devices to no avail. There appears to be no suitable support or advice anywhere. Can anyone help or advise? TIA