There still are a few cardinal-electors who have not yet arrived in Rome. [Cardinal-Elector = less than 80 years of age]. They all must be present to make the decision to set the beginning date for the papal conclave if they wish to convene before March 15.
Meanwhile, Vatican sources are reporting the Sistine Chapel now as being closed to the public to prepare for the space for the conclave. Keep praying for the 115 cardinal-electors, 11 of whom are United States citizens.