The Bluebirds are trying to produce interim payments for your striker, who perished in a plane crash on 21 January.
Cardiff will tell world football’s governing body Fifa that Nantes’ conditions for completion of this offer weren’t fulfilled and Sala wasn’t enrolled as a Premier League player.
Nantes claim the mandatory paper work has been completed.
The French team known the matter to Fifa, who want Cardiff to publish their signs by 3 April.
Sala, 28, was Cardiff’s record signingup, announced on Saturday, 19 January.
The Argentine died when a aircraft piloted by David Ibbotson, who is still missing, crashed into the English Channel near Guernsey.
The team has been due to pay for a first instalment on 20 February.
A Cardiff source said the transfer agreement stipulated – at the request of Nantes – that the Football Association of Wales and France’s Ligue de Football Professional had to ensure the registration to either nightclubs from 22 January, along with confirmation of the worldwide transfer certification released.
The premierleague also had to clean the registration.
The Bluebirds insist the terms of the contract asserts that if any pieces of that arrangement weren’t supported, then the deal could be null and void.
It is thought the notifications clause has been added because when the offer dropped, both Cardiff and Nantes might have had time to look for a fresh player before the January transfer window closed on 31 January.
BBC Sport has also learned arrangements to get a signing-on fee failed to match premier-league rules therefore had been reversed by the league.
Even a Cardiff spokesman would not discuss specific information but said:”The team is mindful of Fifa’s request a reply from 3 April and can be processing that so accordingly. We have no further comment at this point.”
Nantes state that they completed all of the essential paper work and have stated Fifa enrolled the worldwide transfer certification on 21 January.
They state they have been fully compliant with all Fifa’s rules.