The agreement gave the Spanish giants a first-choice option on Maia before a June 30 deadline where they will have to pay an extra £3.2 million to complete the transfer.
But Rai now says Barca have defaulted on payment.
"Sao Paulo, in a week, had the game with Santos with closed gates. The box office of the River Plate game never came, and Barcelona did not pay R $5 million that we were waiting for (for the purchase of Gustavo Maia's priority."
Maia's agent Nilson Moura said of Barcelona signing the youngster: "They came to see him at the São Paulo Cup. He scored three goals and we began to negotiate. They did not even intend to close anything then, but since there was interest from other clubs such as Atlético de Madrid and Liverpool they hurried."