There may be a few reasons that a Location is not displaying on an invoice.

One reason could be that a job location was not chosen when entering a job that creates an invoice. When entering a billing name, there may not be a Location that is linked to the Billing, but is linked to secondary contact details, so it must be selected manually while creating that job. If the job automatically creates an invoice, but there was no location specified in the job itself, then the location in the invoice will not have information that pulls the Location information.

Another reason is if the invoice was manually created, then a location may not have been selected after selecting the Contact or Billing name. There is a dropdown field for Locations, where you can search the location that is connected to the billing name. Because this is an optional field, rather than required, there is no alert to remind you to check the location field is filled out.