Promoted to Italy's top flight this season, Salernitana immediately fell foul of Italian Football Federation (FIGC) rules because they are owned by Claudio Lotito, who also owns Lazio.
Independent directors were appointed in June to organise the club's sale by December 31st but said last week that they had not received good bids and requested a new deadline.
Serie A clubs unanimously voted on Thursday for a postponement of the deadline until the end of the season, but Gravina said after the final FIGC council meeting of 2021 that there would be no extension.
"There is no new ruling. All I did was read the notary deed which provides for the exclusion of Salernitana from Serie A should the club's shares not be sold," Gravina told reporters.
"I hope Salernitana find a buyer before December 31st, otherwise the deed is very clear."