Windows Server 2022 21H2 and 22H2 are two different products that belong to the Long Term Servicing Channel (LTSC) and continuous update releases, respectively.
Therefore, if you are using Windows Server 2022 21H2 edition, you cannot upgrade to 22H2 by installing a patch because it is a different product. You'll need to back up your data and settings before doing a clean install.
Hope the information is helpful.
Best Regards,
Hania Lian
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