The blood also did not liquefy in December 2016.
Cardinal Crescenzio Sepe, the archbishop emeritus of Naples, said Mass in the cathedral to mark the feast day.
When the miracle still did not occur, Sepe told those gathered, "we want to make an act of true and profound devotion to our St. Januarius, we are united in his name."
"It is he who helps us to live, to bear witness to the faith, and even if the blood does not liquefy, it does not mean goodness knows what," the cardinal continued. "The important thing is that we feel truly united, participating in this very special event which is our devotion to our patron saint."
Sepe's resignation as archbishop of Naples was accepted by Pope Francis on Saturday. The 77-year-old archbishop has led the important Italian archdiocese for 14 years.
The 57-year-old Bishop Domenico Battaglia, known as a "street priest" who is close to the poor, was named as his successor.
St. Januarius, or San Gennaro in Italian, is the patron saint of Naples. He was bishop of Benevento in the third century, and his bones and blood are preserved in the Naples cathedral as relics. He is believed to have been martyred during the Christian persecution of Emperor Diocletian.
When St. Januarius' blood liquefied in September, Cardinal Sepe addressed a mostly empty cathedral, due to coronavirus restrictions.
He announced that the blood had "completely liquefied, without any clots, which has happened in past years."
The miracle also occurred in May, when Naples was under lockdown together with the rest of Italy.
Speaking after a livestreamed Mass at the cathedral May. 2, Sepe said: "I have a big announcement to make: even in this time of coronavirus, the Lord through the intercession of St. Januarius has liquefied the blood!"
(Story continues below)
Subscribe to our daily newsletter
This story was updated at 12:32 p.m. Mountain Time to reflect the fact that St. Januarius' blood had still failed to liquefy by the end of the day's celebrations.