Barcelona say Lionel Messi will not be staying at the club “because of financial and structural obstacles”.
Messi, 34, has been a free agent since 1 July when his contract expired.
He agreed a new deal on reduced wages with club two weeks later, but it was dependent on Barca selling players to afford his salary.
“Both parties deeply regret that the wishes of the player and the club will ultimately not be fulfilled,” the club said.
A club statement said: “Despite FC Barcelona and Lionel Messi having reached an agreement and the clear intention of both parties to sign a new contract today, this cannot happen because of financial and structural obstacles (Spanish Liga regulations).
“As a result of this situation, Messi shall not be staying on at FC Barcelona. Both parties deeply regret that the wishes of the player and the club will ultimately not be fulfilled.
“FC Barcelona wholeheartedly expresses its gratitude to the player for his contribution to the aggrandisement of the club and wishes him all the very best for the future in his personal and professional life.”