Issue with Service M8 -Xero integration (Invoice sent marking)

HI.
I have Service m8 used in the field by our techs, and invoices generated in Service m8 are sent to Xero automatically. (All works fine)

However, the invoices that appear in Xero are NOT marked as SENT (even though they clearly are in SM8).
This then causes an issue that Xero's automatic 7/14/whatever day Automatic overdue invoice reminders are not sent to clients as the invoice is not marked as being SENT..

We've just discovered this, and need to resolve this..

Also looking for a bulk way in the mean time to bulk mark invoices in Xero as SENT.. no option apart from going into each individual invoice and marking them as sent which is too time consuming.