Her absentee ballot never arrived. So she flew from Chicago to Pennsylvania to vote.

Helen Wu, a 21-year-old senior at the University of Chicago, requested a mail-in ballot from her home in Montgomery County, Pa., on Sept. 10.

It never arrived. For nearly two months, she went back and forth with election officials in Pennsylvania in increasing desperation, filing additional requests, until this Monday, when she spent hundreds of dollars on a last-minute plane ticket to Pennsylvania to cast her vote for Vice President Kamala Harris.

She is not alone. The New York Times spoke with two other voters in Montgomery County, and a third in Philadelphia, who had similar experiences and had to rush back to Pennsylvania at the last minute to vote.

Ms. Wu provided 12 emails documenting her efforts to obtain a mail-in ballot, as well as screenshots from Pennsylvania’s voter portal. They show that she requested her ballot on Sept. 10, that it was marked as sent, and then that it was marked as “CANC – UNDELIVERABLE.”

She requested another one, but the request was rejected because she had already requested the first, “undeliverable” one. That happened multiple times. After several attempts to contact the Montgomery County voter services offices, she heard back from someone who told her she needed to file a form to cancel the first request. She did that on Oct. 28 — less than five hours after being told to — but did not receive confirmation that the cancellation form had been received until Oct. 30.

On Monday, Nov. 4, now thoroughly panicked, she tried to contact the county voter services office again. This time, she received a response that her ballot would arrive within “24 to 48 hours” — too late for her to return it in time.