Error: "Invoice # must be unique.shopify and xero total price is different"
This error occurs when an invoice with same number is already in Xero and other order with the same number is trying to sync. This error is generated from Xero's end.
Xero does not allow to have more than one invoice with same number. Invoice number must be unique in Xero so you can update the invoice number in Xero to unique number (something other than what’s already in Xero) and then sync this order from Order List >> Unsynced orders page of our app by clicking on "Resync order".
For example, if you already have invoice number #1001 in Xero and later other order with same number #1001 is trying to sync then it will not sync so you will have to update invoice number #1001 which is already in Xero to #1001-1 and then resync the other order.