Beginning June 1, 2024, WhatsApp authentication templates became more restrictive. The most impactful change is that you are no longer able to customize body text in the authentication template (beyond the population of parameters).
The guidelines for authentication templates are included in the article linked above. Additionally, they are included in the authentication templates section of WhatsApp's Guidelines for utility, authentication and marketing templates.
Note that previously-approved authentication templates that do not conform to the new guidelines will now be rejected. You will have to update those templates to conform to the new standards, or create new ones.
