Walk in without an appointment
This surprises people, and it is worth being unambiguous about, because the confusion has a cost. Search for a Chinese consular appointment and you will find sites offering to book one for a fee. There is nothing to book. The counter works by queue number, taken at the door on the day.
The change came with a notice published by the Embassy and all four consulates general at once: the Chinese Embassy and Consulates-General in the U.S. will provide walk-in visa application services starting from October 23, 2023. There's no need to make online appointment beforehand.
What replaces it
The online form does the filtering that an appointment used to do. Your file is reviewed before you are told to come, so by the time you arrive at the counter the office already knows who you are and what you are asking for.
That is why turning up without a COVA file gets you sent away, and why turning up with an approved one usually takes minutes.
What the offices ask of you instead
Dropping appointments moved the burden to preparation.

The counter is fast when the file is complete and slow when it is not, and the reviews of all five offices split almost exactly along that line: people who arrived with an approved application and the barcode page describe twenty-five minutes, and people who arrived hoping to sort it out at the window describe a wasted day.
One reviewer drove in from Kansas to hand over a passport, waited an hour and a half, and was told the submission window had closed the day before. Nothing had been sent by email and nothing appeared in the portal.
For a district that stretches to the Dakotas, checking the status the morning you set off is not excessive.

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