Upgrade Exchange 2019 from CU12 to CU15 Failed

Dear All,

I am have a major issue with hybrid Exchange server 2019, since it failed, the Exchange server has now been offline.

Here it is the error message from the Wizard for upgrade

Error:
The following error was generated when "$error.Clear(); 
          if (($RoleIsDatacenter -ne $true) -and ($RoleIsDatacenterDedicated -ne $true))
          {
            if (test-ExchangeServersWriteAccess -DomainController $RoleDomainController -ErrorAction SilentlyContinue)
            {
              # upgrade the discovery mailboxes to R5 version, this will fix the RecipientDisplayType property of the discovery mailbox which was wrong in R4.
              get-mailbox -RecipientTypeDetails DiscoveryMailbox -DomainController $RoleDomainController | where {$_.IsValid -eq $false} | set-mailbox -DomainController $RoleDomainController
              $name = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxUniqueName;
              $dispname = [Microsoft.Exchange.Management.RecipientTasks.EnableMailbox]::DiscoveryMailboxDisplayName;
              $mbxs = @( get-mailbox -Filter {name -eq $name} -IgnoreDefaultScope -resultSize 1 );
              if ( $mbxs.length -eq 0) 
              {
                $dbs = @(get-MailboxDatabase -Server:$RoleFqdnOrName -DomainController $RoleDomainController);
                if($dbs.Length -ne 0) 
                {
                  $mbxUser = @(get-user -Filter {name -eq $name} -IgnoreDefaultScope -ResultSize 1);
                  if ($mbxUser.Length -ne 0) 
                  {
                    enable-mailbox -Discovery -identity $mbxUser[0] -DisplayName $dispname -database $dbs[0].Identity;
                  }
                }
              }
            }
            else
            {
              write-exchangesetuplog -info "Skipping creating Discovery Search Mailbox because of insufficient permission."
            }  
          }
        " was run: "Microsoft.Exchange.Management.Tasks.RecipientTaskException: The user's Active Directory account must be logon-disabled for linked, shared, or resource mailbox.
   at Microsoft.Exchange.Configuration.Tasks.Task.ThrowError(Exception exception, ErrorCategory errorCategory, Object target, String helpUrl)
   at Microsoft.Exchange.Management.RecipientTasks.EnableMailbox.PrepareRecipientObject(ADUser& user)
   at Microsoft.Exchange.Management.RecipientTasks.EnableRecipientObjectTask`2.PrepareDataObject()
   at Microsoft.Exchange.Configuration.Tasks.SetTaskBase`1.InternalValidate()
   at Microsoft.Exchange.Configuration.Tasks.RecipientObjectActionTask`2.InternalValidate()
   at Microsoft.Exchange.Management.RecipientTasks.EnableMailbox.InternalValidate()
   at Microsoft.Exchange.Configuration.Tasks.Task.<ProcessRecord>b__91_1()
   at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".

And this from the Exchange Log

[05/02/2025 21:38:26.0710] [1] [ERROR] The user's Active Directory account must be logon-disabled for linked, shared, or resource mailbox.
[05/02/2025 21:38:26.0716] [1] [ERROR-REFERENCE] Id=SystemAttendantDependent___590e51a8a98846d3a7fa8ddcc5472c74 Component=EXCHANGE14:\Current\Release\PIM Storage\Discovery 

What I have been trying is that according to this post below

https://community.spiceworks.com/t/exchange-2016-failed-applying-cu-19/793248/18

SUCCESS.

The error log was whinging about discovery but it turned out to be the Search Results mailbox.

I went through every account which looked like it might have something to do with exchange and checked its attribs. Search Results had a corrupt entry. I fixed it and that was that. Back up again!

BOOM

For everyone reading this. If you get this error you need to check each account:

System
Federation
Migration
Discovery
and
Search Results.

I tried every single user account that I'd think Exchange related, updating the HomeMDB with the attribs that found in the DiscoverySearchMailbox, still could not pass the error above.

Any help/ advice would be really greatly appreciated.

Kind Regards