There are instances where carriers send the labels in one file, and this results in shipping labels printing in one batch and followed by the packing slips in another. 

This happens in a batch and/or order with multiple orders and/or packages.

To chronologically print the Shipping label and Packing Slip, enable Redistribute labels (zpl) on the carrier settings. 

Please follow the steps below to configure the account settings:  

1. Go to the Carrier landing 

2. Click on the carrier and go to Account 

3. Edit the Account 

4. On the General tab, check Redistribute labels (zpl) 

5. Make sure to Save changes