1 - Make sure your invoice has an invoice number. Blank invoice numbers create integration issues.
2 - Please make sure all the line items in your job have ledger codes attached. Some accounting softwares, like Xero, will not integrate the invoice if there are line items with missing ledger codes.
To review your job, click "View Ledger Codes" in your Financial tab under the Accounting Bridge section. This will flag the line items in your jobs that do not have ledger codes.
Then, you will need to substitute those line items for line items with ledger codes.
To do this, use the blue plus while inside the job (your Item Catalog) and choose a line item that contains a ledger code.
If you are unsure if the line item has a ledger code, go to Settings < Line Item Catalog. The line items without ledger codes have a red dot.