InPost needs sender details before it can create a label.
For ShipX labels, the sender name printed on the label can come from the Label Sender Name saved in the app settings.
If Label Sender Name is empty, the app keeps the carrier account sender-name behavior instead of inventing a name from Shopify.
The sender phone is saved separately in the app settings.
On Apaczka, the sender is a full address, so a missing street, postal code or city can still refuse the label.