Possible pension error on new employee

Suggested

I had a new employee (start date 25/08/25).  First pay date being 30/09/25, he is over 22 years old and earning £50k.

The pension assessment has not enrolled him, it is saying 'employee is a new starter' and did not take deductions for pay date 30/09/25.

I have done an assessment for pay date 31/10/25 and he is being enrolled 06/10/25 and showing eligible jobholder.

Can anyone shed any light on why he was not an eligible jobholder in that first month?