Unable to update the specified properties for on-premises mastered Directory Sync objects - Updating users manager attribute in azure ad

Having exhaustively search for a solution, I am hoping for some guidance.

I am looking to update users manager attribute which is populated in the on-prem ad but azure/365 don't replicate this as far as I know.

So as I will have to manually change them using the below code;

Set-AzureADUserManager -ObjectId "usersid" -RefObjectId "managersid"

once I run this it fails with the following error;

Code: Request_BadRequest
Message: Unable to update the specified properties for on-premises mastered Directory Sync objects or objects currently undergoing migration.
RequestId: 
HttpStatusCode: BadRequest
HttpStatusDescription: Bad Request
HttpResponseStatus: Completed
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   + CategoryInfo          : NotSpecified: (:) [Set-AzureADUserManager], ApiException
   + FullyQualifiedErrorId : Microsoft.Open.AzureAD16.Client.ApiException,Microsoft.Open.AzureAD16.PowerShell.SetUserManager

I am not sure what the issue is with this as the users manager is synced in azure with windows ad as the source.

Thanks.

According to the docs the Manager attribute is synchronized.

Both the Get and Set cmdlets here need either the DistinguishedName, ObjectGUID, ObjectSID or SamAccountName fot the -Identity and -Manager parameters.

You should be able to do:

# set the manager property for the user
Get-ADUser -Identity "<THE USER>" | Set-ADUser -Manager "<THE MANAGER>"

After that, you can force an AD Sync using something like this:

$server  = 'YourAzureConnectServer'
$cred    = Get-Credential -Message 'Please enter user name and password for AD Sync'
$session = New-PSSession -ComputerName $server -Credential $cred

Invoke-Command -Session $session {
    if (Get-ADSyncConnectorRunStatus) {
        Write-Warning "A sync is already in progress. Please try again later."
    }
    else {
        Write-Host "Initializing Azure AD Delta Sync..." -ForegroundColor Yellow
        try {
            Start-ADSyncSyncCycle -PolicyType Delta -ErrorAction Stop
        
            Write-Host "Waiting for Sync to start.."
            # give the Sync Connector 10 seconds time to start-up
            Start-Sleep -Seconds 10

            Write-Host "Waiting for Sync to finish.."
            While(Get-ADSyncConnectorRunStatus) {
                Write-Host "." -NoNewline
                Start-Sleep -Seconds 5
            }
            Write-Host
            Write-Host "Azure AD Sync has finished." -ForegroundColor Green
        }
        catch {
            Write-Error $_
        }
    }
}

Remove-PSSession $session

^{You can also force a full attribute synchronization by using Start-ADSyncSyncCycle -PolicyType Initial}

Seems like I needed to add a sync rule to the Synchronization Rules Editor - I followed the following - [Link] (blog.kloud.com.au/2016/11/14/…) - I added a rule to sync between ad and azure and back again and this seems to have solved the problem, negating the need for the ps script. - once again thanks to @theo for your help. –