The Italian Football Federation (FIGC) suspended the 33-year-old from football in August after the prosecutor's investigation into Lazio's league meetings with Genoa and Lecce in 2011 determined he had failed to report his knowledge of match-fixing in the latter game.
Mauri resolved to clear his name and return to action for the Roman club he has represented since 2006, but the failure of his appeal on Wednesday evening has invoked a heavier penalty that rules him out until May, meaning he will miss the entire season.
He is expected to pursue the matter with Italy's National Court of Arbitration for Sport.
An FIGC statement also confirmed Lazio's appeal against a 40,000 euro fine - issued in August for their objective liability in the case - had been rejected.
As a result, the FIGC increased the fine to 50,000 euros.
Mauri played as Lazio beat Genoa 4-2 in Rome on May 14, 2011 and eight days later the midfielder featured in a victory by the same scoreline at Lecce.
Prosecutor Stefano Palazzi had originally requested a six-point deduction for Lazio. Lecce, now in the Italian third tier, were fined 20,000 euros in August while Serie A side Genoa were cleared of any wrongdoing.