Mr. Sanders has twice apologized publicly for the incidents — but only in response to media questions following detailed articles — and has promised to do better if he runs again. He is still weighing a 2020 bid, after finishing second to Hillary Clinton in the Democratic race in 2016.

People close to Mr. Sanders have said three of his top advisers from 2016, including his campaign manager, either will not return or will serve in different roles in a future campaign.

A draft agenda included a discussion with 2016 campaign management and facilitators from Working IDEAL, a company that advises on workplace inclusion and diversity. One of the facilitators is Ms. Yang, a former chairwoman of the Equal Employment Opportunity Commission.

Some of the women who have spoken out to reporters about pay disparities, harassment and other instances of discrimination said they were not a part of the planning process for the meeting and were not aware it was happening. Last Friday, concerned that there would be no meeting, some of those women told the Sanders office that they felt it would be unfair to be excluded should a meeting occur, according to emails reviewed by The Times.

On Monday, Mr. Sanders’s office told them it would be arranging travel for them to arrive in Washington by Wednesday. But the women said the office did not send them formal invitations or any details about what would be discussed.

Some of them scrambled to rearrange their schedules, but several women said they did not hear back from Mr. Sanders’s office after being asked for travel details. One of the women was Sarah Slamen, who was the state coordinator in Louisiana in 2016 and who told The Times that she quit Our Revolution, Mr. Sanders’s progressive organization, because of gender discrimination.

Ms. Slamen said she was eventually given a midnight flight back to Texas on Wednesday after the meeting. She declined, she said, because she is six and a half months pregnant. Though she said she would not attend and did not book a flight, she later received a confirmation email for a hotel in Washington.