The Department for Education (DfE) have provided an update on this topic. See below.
We've put in place changes to the application process to make sure particular groups of parents can get eligibility codes by the time they need them. Please see attached the letter from the Entitlements Team with a full explanation.
We've also set out Q&A for parents on our website here: https://educationhub.blog.gov.uk/2024/04/02/how-to-claim-15-hours-free-childcare-code/
For full details please see the attached so you are able to advise parents.