Getting an error when trying to setup Exchange Online ForwardingAddress in Azure Runbook

Question

Hello,

I am trying to setup an Azure Automation Runbook in which I convert a User Mailbox to a Shared Mailbox and setup a ForwardingAddress.

I setup all the permissions and converting the mailbox is working, setting a forwarding address throws the following error:

|Microsoft.Exchange.Data.Directory.InsufficientPermissionsException|Source server:AM0PR08MB4529.eurprd08.prod.outlook.com doesn't have write permission to target DC:. Usually it indicates that target forest isn't an account partition of source forest. The user has insufficient access rights.

This is the script I am using:

Param (
 [string] $Employee = ""
 )

Connect-ExchangeOnline -ManagedIdentity -Organization <DOMAIN>.onmicrosoft.com

$Mailbox = Get-Mailbox -Identity $Employee -ErrorAction SilentlyContinue


if ($Mailbox -eq $null) {}
    elseif ($Mailbox.RecipientTypeDetails -eq "SharedMailbox") {}
    else {
        Set-Mailbox -Identity $Employee -Type Shared -ErrorAction SilentlyContinue
}

Set-Mailbox -Identity $Employee -DeliverToMailboxAndForward $true -ForwardingAddress "<FORWARDING_ADDRESS>" 

If anyone knows a way to solve this please let me know.

Thank you!