The U.S. Mission in China announced that，

The U.S. Mission to China understands that many visa applicants have paid the visa application processing fee and are still waiting to schedule a visa appointment.  We have worked diligently and restored all routine visa operations as of December 17, 2021. For receipts valid on or after March 20, 2020, or purchased between March 20, 2020 and December 16, 2021, the U.S. Mission extended the validity of your payment (known as the MRV fee) until September 30, 2023, to allow all applicants who were unable to schedule a visa appointment as a result of the suspension of routine consular operations an opportunity to schedule and/or attend a visa appointment with the already paid fee.  Fees paid on or after December 17, 2021 are valid for one year from their date of purchase.