On 30 April (US time), Microsoft fixed the error ‘0x80070643’ when installing the January 2024 Recovery Environment Update (KB5034439) in the Windows Server 2022｜Microsoft Learn The company announced that it would not provide a patch. As an alternative solution, a manual fix procedure has been published.

The reason for the failure to install the January 2024 recovery environment update is reportedly due to insufficient free space in the Windows Recovery Environment (WinRE) partition. The required free space is 250 MB, which must be manually reserved if insufficient.

The following procedure can be used to check whether a Windows recovery environment has been configured on the device. If no recovery environment is configured, the device is not affected by this fault.

1. Open the command prompt (cmd.exe) as administrator.
2. run ‘reagentc /info’ If the Windows Recovery Environment is configured, the value of ‘Windows RE status:’ is displayed as ‘Enabled’. If not configured, ‘Disabled’ is displayed.

Microsoft provides the following two guidance on how to change the partition size in a Windows Recovery Environment

… Use a code script to change the partition size (see: ‘Add an update to Windows RE | Microsoft Learn’).
KB5028997: Instructions for manually resizing the partition to install the WinRE update.

Once you have completed either of these steps, you should be able to successfully install the update. It is recommended that you back up the entire disk before doing this, as you may lose all data if you fail to do so.