If your Wix Store is not updating the information after the shipment has been booked, and you have your Wix store connected to a Fulfillment Service, you will want to modify the product information so that you are the fulfiller.
On the left side of the shipment select the eye icon.
Clicking on the eye will bring you to a more detailed overview of that shipment. On the right will be a box with the update status error:
"Received status code 400 while making a POST request to Wix: Array [message] => Invalid request field order message: external app trying to update a fulfillment on items which are associated with another app or with a fulfiller"
To resolve this issue you will need to change the fulfillment service to yourself.
Go to the Store Shipping tab in your site's dashboard.
Under Fulfillment Services select Manage Fulfillment Services.
Select Assign Products to Services.
After selecting your products on the left, select You (self fulfilled) from the dropdown on the right under Choose Service.
Select Done in the bottom right when finished.
If you have not already updated the status in Wix to Fulfilled you can retry in XPS Ship.
Return to the History/Track Tab and selecting "Retry Marking Order as Shipped" from the dropdown arrow next to the shipment. **Note, it may still come up with the same error for the shipments that have already been booked that were previously associated with another fulfiller, or show an error that the order has already been fulfilled. After changing the settings to You (self-fulfilled) the orders you book should no longer come up with that error.