There are troubleshooting that you can do when the invoice is not syncing on Xero
1. Ensure that Xero is properly connected with your Glue Up account on Integrations.
2. Check if invoice mapping has been completed under Account Mapping (e.g. if the invoice is a Custom Invoice, you need to
make sure Custom Invoice mapping is completed in the settings)
3. Check when invoices has been created, as Glue Up Invoices data will be synchronized once per hour.
4. Go to Finance → Invoices, choose the invoices, click Retry Sync Invoice & Payment To Xero and do the same for each