The agency's announcement effectively confirms a further delay to the Flamanville reactor, which was originally scheduled to enter service in 2012.
EDF had said it would begin fuel loading this month before connecting it to the grid in mid-2024.
The company declined to comment on the latest delay.
Repeated delays have sent costs for the project, originally estimated at 3 billion euros ($3.25 billion) when it was announced in 2004, soaring to an estimated 13.2 billion euros by the end of 2022.
EDF needs authorisation from the French Nuclear Safety Authority (ASN) before it can start fuel loading, the ASN added.
In a separate statement released by the agency, it said it was asking EDF to carry out a review of its past supervision of manufacturing activities for equipment intended for its nuclear reactors.
It said earlier this year that it had found 43 cases of fraud in the nuclear sector during 2023, including irregularities at suppliers of equipment for the Flamanville reactor.
