Zagorec was transferred from the prison to that court on Tuesday to give his testimony via a video link, following a request from Argentina, but the link broke down.
The court's spokesman could not say when the new questioning of Zagorec, who is serving a seven year prison term, could be organised.
He also decline to specify the reasons why the Argentine authorities would like to question Zagorec.
Croatian media speculate that this would be about transactions of funds in early 1990s in connection with sales of arms to Croatia.