Do you have your own FedEx account or did you set it up through Shipstation? If you just linked your existing account none of the billing will actually go through Shipstation. You will still need to pay for your shipments/invoices through the Fedex website or by mail if you receive Fedex invoices that way.
Our billing cycle runs through the entire month and I won't see an invoice until next week at some point. Have you tried to reach out to your FedEx rep to see if you're 100% set up. I talked with our rep last week for FedEx, and she's currently working with their IT team to set up an appointment with me to download an API application to my desktop computer. It may be worth reaching out to them and see if they have any advice for you. Sorry I couldn't offer any more help!
Thanks for the response. We are invoiced weekly, and the 1st shipment we sent with Shipstation has been invoiced correctly which is good news. We still don't see these shipments in Fedex Shipmanager though, but can't seem to contact anyone in the IT dept in Fedex to check. Also, the shipment status in Shipstation is not updated, so we can't see which have been delivered. Just not sure if this is how things are meant to be, or if there is a problem.