Seems that Start-ManagedFolderAssistant is not supported on all domains. The setting did not seem to work anyway

src/cmd/purge/scripts/setRetention.ps1

@@ -22,5 +22,4 @@ Connect-ExchangeOnline -Credential $cred
 
 Write-Host "Resetting retention..."
 # Set retention values for all mailboxes 
-Get-Mailbox | ForEach-Object { Set-Mailbox -Identity $_.Alias -RetentionHoldEnabled $false  -LitigationHoldEnabled $false -SingleItemRecoveryEnabled $false -RetainDeletedItemsFor 0 -AuditLogAgeLimit 0 -Force }
+Get-Mailbox | ForEach-Object { Set-Mailbox -Identity $_.Alias -RetentionHoldEnabled $false  -LitigationHoldEnabled $false -SingleItemRecoveryEnabled $false -RetainDeletedItemsFor 0 -AuditLogAgeLimit 0 -Force }
-Get-Mailbox | ForEach-Object { Start-ManagedFolderAssistant -Identity $_.Alias }