Hello. We recently upgraded Order Ship Express to 1.1 due to the issues described in a different forum post. As soon as we did, we no longer have the OSE functionality on the Sales Order Shipment page 10026. We no longer see the page extension load on this page. Can you check?
The current resolution is to create a separate extension to embed Order Ship Express within the Sales Order Shipment. We have an example extension available here. Your partner may want to roll this into one of their extensions, or change some of the properties within the app.json or object naming.