If you are automatically pushing invoices to ServiceM8 and you receive an error message with an X icon of "Store setting does not allow items to be pushed to ServiceM8".

This means that in your default ServiceM8 settings, you have selected Suppress Line Items to ServiceM8 and you haven't ticked Upload Invoice and/or Delivery Dockets to ServiceM8. 

To rectify this, you have to choose between sending line items to ServiceM8 only, sending the PDF invoice only, or pushing both line items and PDFs.