Xero: To update fields on a paid invoice line item, you must supply a LineItemID

100000001: Export did not succeed | Errors received from Xero: A validation exception occurred| To update fields on a paid invoice line item, you must supply a LineItemID| The status AUTHORISED cannot be applied to the invoice because it has payments or credit notes allocated to it.

The error message usually indicates that:

1. Xero already has this invoice number (from Magento or other source) and
2. and a payment has been applied against it.

Any further changes to that invoice are then prevented by Xero with the above error message. We suggest taking a look at the invoice history in Xero (see below) to establish if this invoice had already been exported by our integration, was possibly exported wrongly from a test site (we suggest connecting any test/staging/dev sites to a Xero demo organisation to prevent this from happening) or is genuinely a double up of order numbers.

If the invoice in Xero matches the one in Xero you can fix up the export status in Magento by selecting the invoices showing Attempted but Failed and using the action "Link Selected".

All other double ups would need to be investigated further to ascertain its origins vs what order numbers your store uses.