Cardiff were claiming more than 120m euros (£104m) for loss of income and other damages, based on the belief Sala could have kept the club in the Premier League.
But the Nantes commercial court dismissed its claims and also ordered the Welsh club to pay about £400,000 in legal fees and moral damages suffered by the French side.
The penalty was payable immediately, regardless of any possible appeal.
At the time of the verdict, Cardiff’s legal representatives said they would take time to reflect whether to continue the legal claim via an appeal, that would be heard at the Court of Appeal in Rennes.
Cardiff had a three-month window to decide – with the deadline this week – but the club has now confirmed they have lodged their intention.
An appeal triggers a new trial – a second chance at the case being heard and re-examined in its entirety – with the process taking up to two years.
