Sorry, I selected the answer as solved and it’s not.
Dear John, I confirm that the field key is the repeater one, and that the repeater is not nested in any other field.
I firstly use add_row(), and nothing happens.
I checked if acf was active in the template where I have this problem and it was…
I finally solved the issue, using native wp functions, and building the repeater registers in post_meta with add_postmeta or update_postmeta, it has been a lot more work, but I was in a hurry and needed to solve it quickly.