Matuidi revealed after Juve's 1-0 win in Sardinia on Saturday that he had been the subject of racist chanting, with Cagliari issuing an apology to the 30-year-old French player the following day.
But Lega Serie A's disciplinary report released on Tuesday found that "no determination can be made with regard to Cagliari for the deplorable expressions of racial discrimination of which Juventus player Blaise Matuidi reports he was the subject".
"No sanction can be brought [because] those expressions were not heard by either the match referee nor by [Italian football federation] FIGC employees, nor filed in the match report."
After hearing abuse from the stands Matuidi rushed to referee Giampaolo Calvarese, but the official ignored his pleas to intervene and Medhi Benatia and Paulo Dybala had to calm their teammate down.
Matuidi was born in France to an Angolan father and a Congolese mother.
Saturday's abuse follows similar racist chants directed at Matuidi during Juve's 3-1 win at Verona late last month, for which Verona were fined €20,000 by the Italian league.
Elsewhere Napoli were fined €15,000 on Tuesday after fans threw firecrackers at visiting Verona fans in last weekend's game, with Roma fined €10,000 for throwing objects onto the pitch, and an additional €3,000 for Atalanta's coaching staff having a laser light shone in their direction.
Atalanta were also fined €5,000 after their coach Gian Piero Gasperini relayed instructions to his coaching staff having been banished to the stands.