Hi @Георгий Гурушкин ,
Was the DC installed on the main domain?
And for your situation, you should better use PrepareAllDomains
I guess the users are on your main domains and that could be the reason you get this error:
Please check this document and focus on this:
- You need to prepare every domain where an Exchange server will be installed.
- You need to prepare any domain that will contain mail-enabled users, even if the domain won't contain any Exchange servers.
- Your account needs to be a member of the Domain Admins group in the domain that you want to prepare.
- If the domain that you want to prepare was created after you ran /PrepareAD in Step 2, your account also needs to be a member of the Organization Management role group in Exchange.
You could check the version after preparing all domains and if that shows the old one, please try installing the update again.
And a suggestion is to install the latest CU22 while not CU21, there are many security patches included in CU22, and better install the latest SU here:
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