INDIANAPOLIS — The College Football Playoff’s ambitions for expansion stalled on Monday, when the sport’s leading power brokers proved unable to agree on a plan almost seven months after some of them publicly proposed a 12-team format.

The playoff, which features four teams each season, could still grow in the coming years and annually inject hundreds of millions of dollars more into the richest conferences in college sports. But the addition of games as soon as the 2024 season is increasingly unlikely after months of turmoil, with the negotiations complicated at different moments by disputes over potential compositions of the playoff field, fears of protracted seasons and mistrust that flowed from a surprise round of conference membership shuffles.

Three days of meetings in Indianapolis, where the playoff’s 11-person management committee convened ahead of Monday night’s national championship game between top-ranked Alabama and No. 3 Georgia, ended hours before the game without the unanimity required to make significant changes to the playoff.

“Have you ever seen the movie ‘Groundhog Day’?” Big 12 Commissioner Bob Bowlsby said after the latest set of meetings concluded on Monday.

Most commissioners and college leaders left through alternative exits or brushed past reporters, directing them to speak with Bill Hancock, the playoff’s executive director, and Mississippi State President Mark Keenum, the chairman of the playoff’s board of managers — the panel of university presidents and chancellors who oversee the management committee.

Bowlsby, though, could not contain his exasperation.

Although he did not slam the door on an outcome that would increase the size of the playoff before the current agreement’s expiration at the end of the 2025 season, Bowlsby suggested that the chances for a speedy accord were vanishing. He signaled that at least some opposition to the 12-team proposal he helped craft — a plan to offer bids to the six highest-ranked conference champions, plus six at-large teams — appeared intractable so far.

“Let me just say there’s more parochiality than there needs to be,” said Bowlsby, the longest-tenured commissioner of a Power 5 conference. “Everybody is more concerned about their own silo than everybody else’s,” he added.

There are three recently appointed conference commissioners: the Big Ten’s Kevin Warren, who arrived two years ago, as well as the Pac-12’s George Kliavkoff and the Atlantic Coast’s Jim Phillips, who took their positions last year.

They were among those taken aback when a plan developed by Bowlsby, SEC Commissioner Greg Sankey, Mountain West Commissioner Craig Thompson and Notre Dame Athletic Director Jack Swarbrick was sprung last June on other committee members (and the public) as something of a fait accompli.

The objections centered around several subjects. One was the size of the playoff field; Phillips, for example, said recently he would only support an expansion to eight teams, and he was not in favor of any alterations until the N.C.A.A. finishes rewriting its constitution, which could happen next week. Other worries were related to how many berths would be guaranteed and what would happen to existing bowls.

In a statement on Monday evening, the Pac-12 said it backed the six “most-discussed” formats, including a system in which the 12 highest-ranked teams would earn playoff slots and another that would award bids to the Power 5 champions, the top Group of 5 champion and six at-large teams. The league also said it was open to proposals for an eight-team format, like one that would include the eight highest-ranked teams.

But there is entrenched opposition to an eight-team approach.

“It is clear none of the six most-discussed expansion models has unanimous consent, with most having considerable opposition, and every conference other than the Pac-12 has indicated that they would be against at least one of the proposed models,” the Pac-12 said.

Sankey, who spoke with reporters more than an hour after Monday’s final meeting broke up, said he found it perturbing that some conferences that beat the drum to expand three years ago were now objecting to a proposal to do just that.

“I genuinely never assumed this would just be a rubber stamp, but I also know that when issues are identified, there has to be a resolve to work to solutions and there have to be solutions identified,” said Sankey, who would not identify which commissioners he was speaking about.

He also said that if the negotiations went back to the start, there would be no guarantee that the SEC would be willing to make whatever concessions it was willing to make now.

Any optimism for change was built around the enormous financial windfall that a larger tournament would deliver to the leagues. There are also substantial frustrations with the current system, which debuted in the 2014 season and replaced the Bowl Championship Series.

Just 13 universities have made playoff appearances, and some of them, like Alabama, Clemson and Ohio State, have repeatedly been contenders. (The 2017 season ended with an Alabama-Georgia title game as well.)

Also, entire conferences — indeed, most of the ones that run the playoff — have always or regularly been excluded. This season was the first time that a Group of 5 league had a team earn a playoff berth, when Cincinnati was ranked fourth. Central Florida was excluded in 2017 and 2018 despite posting undefeated regular seasons, just like Cincinnati was in 2020.

But in addition to concerns around the games and competition formats, some administrators fretted that the leagues would sacrifice millions of dollars if the playoff expanded before its television deal could hit the open market. Deepening tensions, a new wave of private maneuvering and open sniping consumed college sports after Oklahoma and Texas announced plans to leave the Big 12 for the SEC.

If and when the playoff expands, a new media rights deal could make it the most lucrative college sports event, surpassing even the Division I men’s basketball tournament.

The playoff and its three games each season are currently included in a 12-year deal with ESPN worth more than $5.6 billion. Consultants estimate that an expanded tournament of 11 games a season would attract more than $1 billion a year in television rights alone; by comparison, the rights for last year’s N.C.A.A.’s men’s basketball tournament, a 67-game showcase, pulled in more than $850 million.

Television rights are just part of what an expanded playoff could fetch. Combined with sponsorships and ticketing, the 12-team format could offer more than $2 billion in annual income, according to a projection by Navigate, a sports business consultancy.

Asked what it said about the process that an agreement on something as simple as a playoff format could not be reached, Keenum, the Mississippi State president, said it was not simple.

“For the average layperson, if you will, the sports fan, yeah, why not?” Keenum said. “Twelve teams. Sixteen teams. Thirty-two teams. Whatever teams. How big a deal is that?”

But, he noted, there were complex matters to be resolved. “It’s not just one school or one conference,” he said. “You’ve got schools across the country that have a stake in this.”