Office 365 Outlook Online Archive Not Processing

With Powershell, run the following to remove any retention holds and also start the auto archive to online archive.

Install-Module -Name ExchangeOnlineManagement
Import-Module ExchangeOnlineManagement
Connect-ExchangeOnline -UserPrincipalName adminuser@office365domain.com
Set-Mailbox 'adminuser@office365domain.com' -RetentionHoldEnabled $false
Start-ManagedFolderAssistant -Identity 'username@office365domain.com'

This was recommended by the help tool within the Exchange section in Office365 portal:

https://learn.microsoft.com/en-us/powershell/exchange/exchange-online-powershell-v2?view=exchange-ps#powershellget-for-rest-api-connections-in-windows